*U.S. official says Taliban ambushed chopper with rocket-propelled grenades
*Common technique rarely brings down aircraft
*Fatal attack does not point to increased sophistication of the Taliban
*Chopper was on its way to aid other elite troops fighting militants
*Twenty-two of the dead soldiers were from elite Seal Team Six
*At 38 deaths in total, it's highest number of U.S. casualties in one incident
*President Obama mourns 'extraordinary sacrifice'
Lives lost: Lt Cmdr Jonas Kelsall (L) and Chief Petty Officer Robert James Reeves (R), both Shreveport, Louisiana natives who were killed when a U.S. Chinook helicopter crashed in Afghanistan on Saturday
They were inseparable high school best friends, who stuck together through remarkable triumph - and the bitterest of tragedies.
As the U.S. comes to grips with the deadliest loss of American lives since the war in Afghanistan began, it has emerged that among the 38 brave men who perished were two home town best friends.
Chief Petty Officer Robert James Reeves and Lieutenant Commander Jonas Kelsall, from Shreveport, Louisiana, both mastered extreme trials to gain their places on Seal Team 6, the elite unit which killed Osama Bin Laden just three months ago.
They had excelled at high school together before enlisting and being sent to Afghanistan, where the pair were assigned the same mission, placed in the same helicopter - and died together when the Chinook was shot down in an attack on Saturday morning.
Mr Reeves, 32, joined the elite Seal team in 1999. He had been best friends with Mr Kelsall, who enlisted soon after, since his freshman year of high school.
'He was always very gregarious, a star soccer and lacrosse player in high school,' Mr Reeves's father, James Reeves, told the New York Times.
'It had never been obvious to me that he was going to choose a military career. It is very difficult to make it on these Seal teams. But that was where he knew he needed to be.'
In more than a decade of service, Chief Reeves fought in war zones more than a dozen times. He earned four Bronze Stars for bravery, each with a 'V Device', signifying valour.
His family last saw him at home for Christmas but even then he refused to speak about the highly secretive specifics of his work, his father said.
The Chinook chopper which crashed early on Saturday morning was on a mission to back up U.S. Army Rangers, who had come under fire by Afghan insurgents in the area.
The team had completed their mission to subdue the attackers, and were departing in the helicopter when it was hit by a rocket-propelled grenade.
Tragic: Sgt Patrick Hamburger, 30, of Grand Island, Nebraska (L) and fallen Service Man Kevin Houston (R), both of whom were killed in action
Heroes to the end: Navy SEAL Michael Strange (L) was on his third tour of Afghanistan; Spencer Duncan of Olathe, Kansas (R), was serving as a door gunner on the helicopter when it was shot down
Proud: Aaron Carson Vaughn (L) is one of the elite soldiers who was on the doomed chopper; Air Force Tech Sgt John Brown (R) was a paramedic whose unit was attached to the Navy SEALs
However, a U.S. official has said news of the deaths does not signify increased sophistication of the Taliban, calling the fatal attack a 'lucky shot'.
'We are not seeing it as a game changer,' an unnamed official told the Telegraph. 'This was not a new tactic and it wasn't a new weapon.
A spokesman for the Taliban movement said the craft had been shot down with a rocket-propelled grenade (RPG) from as close as 150yds in an ambush attack soon after it took off following the raid.
Ambushing aircrafts is a common tactic of insurgents in parts of southern and eastern Afghanistan, making the aircraft vulnerable during take-off.
Another official, who spoke on condition of anonymity to describe the event while the investigation remains ongoing, said that the Rangers, special operations forces who work regularly with the SEALs, secured the crash site afterwards.
38 people - including 30 American Special Forces troops and eight Afghan soldiers - were killed when the blast brought down the helicopter early Saturday.
Of the 30, 22 Navy SEALs from the elite 'Team Six' unit that killed Osama bin Laden lost their lives.
On Sunday, the names of the Americans aboard the chopper began to be released.
Aaron Carson Vaughn, from Tennessee, was a 30-year-old Navy SEAL and the first special ops soldier to be identified in the devastating crash that killed 38 on Friday.
He left behind two children, the couple's two-year-old son, Reagan, and two-month-old daughter, Chamberlyn.
Tragic development: U.S. President Barack Obama holds a conference call from Camp David, Maryland yesterday after a NATO helicopter crashed during a battle with the Taliban in Afghanistan
Widow Kimberly Vaughn saw television reports of the helicopter downed in Afghanistan on Saturday morning, before her doorbell rang and Navy officers told her that her husband was killed in action.
In spite of her pain-staking grief, she said her husband 'wouldn't want to leave this Earth any other way than how he did' - making the ultimate sacrifice for his country.
'He loved his job,' she told CNN. 'There was no way - even if you could tell him that this would have happened he would have done it anyway. All those men are like that. They're selfless.'
It was just hours before the fatal mission Vaughn had called his wife, and spoke to his son for the last time.
'It was actually a great conversation - probably just about time before he went out to work that night,' she remembered. 'We got to tell each other we loved each other, so it was a great conversation to have.'
Soon after, the tragedy came to her doorstep.
'I thought, "Oh, hopefully it's just a neighbour," and as I rounded the stairs I saw the men in uniform and I just fell to my knees. There's no preparing for it. It's something you see in the movies. It's not something you're supposed to live through.
'I fell to my knees and cried and didn't want to hear it, but it's the truth,' she remembered. 'You want it to be a mistake. You want them to say it's the wrong person, but I wouldn't wish this on anyone.'
A family from the Philadelphia area was devastated to learn their son, Navy SEAL Michael Strange, was also killed.
His father, Charles Strange told CBS Philly: 'He was intense, he was funny, he had that dry humour, like Seinfeld.'
Sgt Patrick Hamburger, a Navy SEAL from Lincoln, Nebraska, spoke to his family back home before the mission.
He told his brother that he wouldn’t be in touch because his team 'had stuff to do.'
Kevin Houston of Chesapeake, Virginia, died while living his dream.
The 36-year-old had wanted to be a SEAL since he was a toddler, friends told The Boston Globe.
Grieving parents in Jacksonville, Florida, confirmed to the Jacksonville Daily News that their son, Navy SEAL Chris Campbell, was on the chopper when it was shot down.
Another SEAL, Jon Tumilson, of Rockford, Iowa, perished in the crash, his father said.
Spencer C Duncan, 21, of Olathe, Kansas, was serving as a door gunner on the doomed chopper when it was brought down.
Air Force Tech Sgt John W. Brown of Arkansas, a paramedic whose unit was attached to the Navy SEALs, made the ultimate sacrifice.
Kraig Vickers, a Navy bomb disposal team member, of Haiku, Maui, also died in the attack.
Revenge? Some analysts peculated that the attck could be seen as retaliation for the killing of Al-Qaeda mastermind Osama bin Laden by Seal Team Six
Return trip: 23 Seals who killed Bin Laden in his Pakistan compound in May had recently returned to Afghanistan from their base in North Carolina
Childhood friend Mike Labuanan of Wailuku told Hawaii News Now Vickers was planning to return to the islands next year.
'We e-mailed a few times several weeks ago, and he let me know that he was having another child and moving back to Oahu.
'Kraig is real strong, real smart,' he said. 'And he always wanted to do something challenging, so when he said he was going into the Navy, it was only right. It kinda fit his personality.'
Meanwhile, as Nato begins an operation to recover the remains of the large helicopter, an Afghan official says heavy fighting has erupted in the area of the crash.
Wardak provincial spokesman Shahidullah Shahid said Sunday that a joint operation was taking place in the Tangi Joy Zarin area of Sayd Abad district.
He said there were reports of Taliban casualties overnight, but had no additional information.
It was reported last night that the Seals who died in the helicopter crash were not among the 23 who killed Bin Laden.
According to intelligence officials, the 23 SEALs who killed Bin Laden at his compound in Pakistan in May had recently returned to Afghanistan from their base in North Carolina.
However, they were members of the same 120-strong SEAL Team Six and would have trained alongside and been close friends with those who carried out the Bin Laden raid.
It was not clear if the Taliban had deliberately targeted the helicopter as an act of revenge.
Vulnerable: Slow-moving transporter craft like the Chinook face massive risks in eastern Afghanistan
Mystery: It was reported those who died were not among the 23 Seals who killed Bin Laden
But its shooting down is bound to be greeted in many parts of the Arab world as terrible vengeance for the death of the Al Qaeda leader.
Reports suggested that seven members of the Afghan National Army, one dog handler, an interpreter and an unknown number of crew were also on board the downed helicopter. Friday night’s attack is the deadliest single incident since the Afghan war began in 2001.
It was also the highest one-day death toll for US Navy Special Warfare personnel since the Second World War. In 2005, 16 Navy Seals and US Army special forces troops died when their helicopter was shot down as they tried to rescue four comrades under attack from the Taliban.
'A Nato helicopter crashed last night in Wardak province,' Karzai said in the statement, adding that 31 American special operations troops were killed.
'President Karzai expressed his deep condolences because of this incident and expressed his sympathy to Barack Obama.'
Mr Obama, who learned of the incident at Camp David, issued a statement saying his thoughts and prayers go out to the families of those who perished.
'Their deaths are a reminder of the extraordinary sacrifices made by the men and women of our military and their families, including all who have served in Afghanistan,' the president said.
'We will draw inspiration from their lives, and continue the work of securing our country and standing up for the values that they embodied.'
Mr Obama said he also mourned the loss of seven Afghans 'who died alongside our troops in pursuit of a more peaceful and hopeful future for their country.'
At the Pentagon, Defense Secretary Leon Panetta says he is deeply saddened by the loss, and vowed that the U.S. will stay the course to complete the mission to make the world a safer place.
The Chinook involved in Friday’s attack – a US twin-engined helicopter mainly used to transport troops – was hit by a shoulder-held grenade as it returned from a night raid on a militant gathering in the Tangi Valley in Wardak province, west of Kabul.
The Tangi Valley, dubbed ‘Death Valley’, is known for being one of the most hostile corridors in Afghanistan. The volatile Wardak province is an infamous insurgent stronghold.
The Special Forces unit in the Bin Laden operation, Seal Team Six – known as the Naval Special Warfare Development Group – has around 300 members, of whom 120 are commandos. The rest are communications and specialist support troops.
US sources said the troops were being flown by a crew of the 160th Special Operations Aviation Regiment. The Taliban claimed they downed the helicopter with rocket fire and that wreckage was strewn at the scene.
The tragedy comes as America draws down its presence in Afghanistan and attempts to hand over responsibility for security to Afghan forces. Seven Afghan soldiers were also killed in the crash.
'Their deaths are a reminder of the extraordinary sacrifices made by the men and women of our military and their families, including all who have served in Afghanistan,' he said in a statement, adding that his thoughts and prayers go out to the families of those who perished.
Defense Secretary Leon Panetta said: 'Their courage was exemplary, as was their determination to make this a safer world for their countries and for their fellow citizens. We will stay the course to complete that mission, for which they and all who have served and lost their lives in Afghanistan have made the ultimate sacrifice. They and their families are in my thoughts, in my prayers and in my heart.'
Unforgiving terrain: The Taliban-infested, rocky valleys of the Wardak province where the helipcopter was brought down
Elite: The Navy Seals are the special operations unit that killed Osama Bin Laden
Aircraft crashes are relatively frequent in Afghanistan, where insecurity and difficult terrain make air travel essential for coalition forces transporting troops and equipment.
There have been at least 17 coalition and Afghan aircraft crashes in Afghanistan this year.
In June 2005, 16 American troops were killed when a U.S. helicopter crashed in eastern Kunar province after apparently being hit by a rocket-propelled grenade.
Most of the crashes are attributed to pilot errors, weather conditions or mechanical failures. However, the coalition has confirmed that at least one CH-47F Chinook helicopter was hit by a rocket propelled grenade on July 25, injuring two crewmembers.
Meanwhile, Nato troops attacked a house and inadvertently killed eight members of a family, including women and children, in the southern Helmand province, an Afghan government official said Saturday.
THE FIVE DEADLIEST MILITARY CRASHES IN AFGHANISTAN
Excluding the latest, and worst, crash, they are:
June 28, 2005: U.S. helicopter is shot down in eastern Kunar province during a rescue operation, killing 16 special operations troops.
April 6, 2005: U.S. Chinook helicopter crashes in a sandstorm near eastern Ghazni, killing 15 American troops and three civilian contractors.
May 5, 2006: U.S. Chinook helicopter crashes while attempting a night landing on a small mountaintop in eastern Kunar province, killing 10 U.S. soldiers.
September 21, 2010: U.S. Army Blackhawk crashes in southern Zabul province, killing nine troops on board, including four Navy Seals.
February 18, 2007: U.S. Chinook carrying 22 U.S. soldiers crashes in southern Zabul province, killing eight and injuring 14.
Nato said Taliban fighters fired rocket propelled grenades and small arms at coalition troops during a patrol Friday in the Nad Ali district.
The troops fired back, and as the fight escalated an aistrike was called in against the Taliban position, said Brockhoff, the NATO spokesman.
He said Nato sent a delegation to meet with local leaders and investigate the incident.
Nad Ali district police chief Shadi Khan said civilians died in the bombardment but that it was unknown how many insurgents were killed.
Taliban spokesman Zabiullah Mujahid said: 'The fresh reports from the site tells us that there are still Americans doing search operations for the bodies and pieces of the helicopter are on the ground.'
Gen. Abdul Qayum Baqizoy, police chief of Wardak, said the operation began around 1 a.m. Saturday as Nato and Afghan forces attacked a Taliban compound in Jaw-e-mekh Zareen village in the Tangi Valley.
The firefight lasted at least two hours, the general said.
Sympathy: Afghan President Hamid Karzai offered his condolences to President Obama.
'It was at the end of the operation that one of the Nato helicopters crashed,' he said.
'We don’t know yet the cause of the crash, and we don’t know how many Nato soldiers were on board.'Helmand, a Taliban stronghold, is the deadliest province in Afghanistan for international troops.'
Nato has come under harsh criticism in the past for accidentally killing civilians during operations against suspected insurgents.
However, civilian death tallies by the United Nations show the insurgency is responsible for most war casualties involving non-combatants.
Also in the south, Nato said two coalition service member were killed, one on Friday and another on Saturday. The international alliance did not release further details.
The deaths bring to 334 the number of coalition troops killed this year in Afghanistan, and 11 this month.
WHO ARE THE U.S. NAVY SEALS?
U.S. Navy's SEa, Air and Land Teams, (SEALS) are the U.S. Navy's principal special operations force and a part of the Naval Special Warfare Command (NSWC) as well as the maritime component of the United States Special Operations Command (USSOCOM).
The name is derived from their capacity to operate at sea, in air or on land, but in the war on terror they have been almost exclusively for land-based operations, such as the storming of Osama bin Laden's compound.
The Seals were born in the Second World War when the Navy recognised the need for soldiers to take control of landing beaches, note obstacles and defences, and ultimately guide the landing forces in.
The unit officially became known as the Naval Combat Demolition Unit.
They became Seals in 1961 when President John F. Kennedy, aware of the situations in Southeast Asia, recognized the need for unconventional warfare and special operations as a measure against guerilla warfare.
Units were established to operate from sear, air or land.
The first joint Seals and CIA operations, which are currently being carried in the war on terror, were executed in the Vietnam War.
Since then the SEALS teams have operated in Grenada, the Persian Gulf and Panama.