In the weeks before his death, 21-year-old Mabry Anders had grown increasingly worried that he might not come home from Afghanistan. The army specialist was battling insomnia and would send brief, worried messages back to his family.  

“He talked to me in the day, which would be in the middle of his night,” his father, Dan Anders, said. “He didn’t sleep. He was just worried.”

There were good reasons for concern. During his six-month tour, the Taliban staged a major attack at his base, a suicide bomber had killed one of his brigade’s most revered leaders, and an Afghan villager threw a fire-bomb at a vehicle he was traveling in.

But what Anders may not have expected is that his killer would be an Afghan army soldier, one of those the US military is supposed to be training to take over security of the country ahead of the withdrawal of most US troops by the end of 2014.

A surge in insider attacks (also known as green on blue attacks) has prompted Nato to temporarily curtail some joint operations. The move casts doubt on what exactly international forces can accomplish in those places where they cannot work alongside their Afghan allies.

Interviews in Afghanistan and the United States have uncovered new details about the attack on August 27, which also took the life of another US soldier, Sergeant Christopher Birdwell. These include Taliban claims that the insurgents prepared the Afghan soldier for the killings.

“After the shooting incident a group of Taliban came to my house and said that Welayat Khan was their man,” said Nazar Khan, the brother of the Afghan soldier who was killed by US forces after he opened fire on the Americans.

“‘We have trained him for this mission and you must be proud of his martyrdom,’” the brother quoted a local Taliban commander as saying.

Interviews with Afghan officials suggest that Welayat Khan was not properly vetted. He was admitted to the force seven months before the attack, despite presenting a fake birth certificate and having gotten a flimsy recommendation from a commander who vouched for him simply because the two men were ethnic Pashtuns, according to Afghan sources speaking on condition of anonymity.

Insider attacks now account for one in every five combat deaths suffered by Nato-led forces in Afghanistan, and 16 per cent of all American combat casualties, according to 2012 data. The rising death toll has alarmed Americans and raised new, troubling questions about the unpopular war’s direction.

The Pentagon is promising better vetting of Afghan recruits like Welayat Khan, and Nato last week announced it was scaling back cooperation with Afghans to reduce risk to Western troops.

That includes Anders’ unit, stationed at Combat Outpost Xio Haq in Laghman province, in eastern Afghanistan, which, for the moment, has halted joint operations.

But it’s unclear whether the United States or Nato or the Afghan government forces they’re training will be able to stop the next Welayat Khan before he strikes.

“Save us from the infidels” Khan was raised in a deeply religious family in the mountain village of Shor Khil, a collection of about 100 mud-built houses near the Tora Bora mountains not far from the Pakistan border.

Relatives said they were taken by surprise when he joined the Afghan army. His cousin Rahman recounted that Welayat had lambasted Western military forces.

“Welayat had a small radio and liked to listen to news about Afghanistan. He became very upset and angry when there were reports about civilians being killed by air strikes,” Rahman said. “‘May Allah save us from the hands of these infidels,’” he quoted Welayat as saying.

According to family members, Welayat had shown signs of mental instability since an accident at work when he slipped on a mountain while breaking rocks for construction. Nazar Khan, Welayat’s older brother, said he would suffer mental breakdowns and “get angry at minor things.”

In Welayat’s pictures, provided by his brother Nazar Khan, he appears clean-shaven, young, stern looking, with a mass of thick black hair. He has a long face and slender build. In one picture he is gently holding his green beret in his right hand, with his left hand resting on the barrel of a machine gun.

Work with the Afghan army meant steady paychecks of about $240 a month, helping his 15-member family. Still, his relatives asked him to quit out of fear of reprisals by the Taliban, who have warned villagers not to join the Afghan security forces.

“We have all warned him to leave the army and find another job,” Rahman said.

Reprisals from the Taliban, it turns out, wouldn’t be a problem.

In cold blood Although the Taliban claim to have trained Khan for his mission, there is nothing to suggest at this point that he knew where, when or even if he would strike on the morning of August 27. By all accounts, he did not know the two US soldiers he shot.

Anders, an Army mechanic from a small town in Oregon, and Birdwell, from Windsor, Colorado, were part of an early morning clearance mission near the Afghan town of Kalagush when the lead vehicle in their convoy hit a bomb.

Improvised explosive devices, or IEDs, are hardly a novelty and, after 11 years of war, troops know how to respond. Soldiers in the convoy quickly secured the area and Anders went to help load the damaged vehicle for transport.

The American patrol had the road blocked to ensure security. But the Afghan soldiers approaching in another convoy were not seen as a potential threat, and were allowed to pass. On board that convoy was Welayat Khan.

“They are trained to trust the Afghan soldiers,” Anders’ mother, Genevieve Woydziak, said.

Welayat Khan was sitting at the gun turret mounted on a vehicle in the Afghan convoy. At 8:10 in the morning, as his vehicle passed Anders and Birdwell, Welayat Khan took aim at the Americans and fired.

“The rest of the Afghan soldiers at that point laid their weapons down” to avoid being shot, Woydziak said.

Welayat Khan then jumped out of the Afghan vehicle and started to run. But he didn’t get very far.

An American helicopter arrived in minutes and shot Khan dead less than a kilometer away, according to a US Army spokesman.

Khan’s older brother said the body was so riddled with bullets that it was unrecognizable.

“The coffin was sealed,” Nazar said, adding that the government declined to provide any money for the funeral because of Khan’s links to the Taliban.

In hunting for an explanation, Reuters learned of an alternative narrative. Khan’s brother heard from Afghan forces and an Afghan eyewitness that there was a dispute at the American roadblock, involving a pregnant women who needed to pass. In this scenario, an American at the scene told her to wait and Khan retaliated.

“My brother is a martyr and the whole family is proud of his martyrdom but we blame the Americans for inciting him to shoot,” Nazar Khan said.

But a US Army spokesman said there was no indication so far that Khan had any interaction with the American soldiers he killed, or with any of the other American forces, for that matter. The Army investigation is ongoing.

The Taliban appears to be claiming they were in on the attack from the start, before Welayat Khan even joined the army.

“Mullah Abdul Samad and his men came to my house a day after I buried my brother and they were saying that Welayat joined them before enrolling in the army,” Nazar Khan said, referring to the village Taliban commander.

It’s unclear what, beyond perhaps Welayat Khan’s fake birth certificate, Nato might have caught with its newly enhanced steps to weed out dangerous Afghan soldiers, announced in the weeks after the shooting.

Many of the attacks are chalked up to personal grudges, in a country where disputes are frequently settled at gunpoint and where asking after a wife’s health could be seen as offensive.

Brigadier General Roger Noble of Australia, deputy chief of staff of operations in Afghanistan, said Nato was working on creating “shooter profiles” from past cases to see if it is possible to identify worrying traits or characteristics.

Ryan Crocker, US ambassador to Afghanistan until July, warned that “the Taliban have found a niche.”

“I think they’re finding that ... relatively easy to do,” he said at an event hosted by the Carnegie Endowment for International Peace. “And our own vetting in the US military is not that great, let’s face it.”

Taliban spokesman Zabihullah Mujahid, speaking by phone from an undisclosed location, told Reuters that “a large number” of fighters have infiltrated the Afghan security forces.

“A hero comes home” Anders’ mother was at her office on August 27 when she got a call from workers at her house in Baker City, Oregon. They told her that two Army soldiers had arrived at her doorstep.

“I served in the Army myself. We knew why they were there,” she said.

It was a long, 15-mile drive back to her home, where she would learn with certainty about her son Mabry’s death earlier that day on the other side of the world. She has learned more details about it since then.

The parents are still wrestling with agonizing questions.

Dan Anders, Mabry’s father, who lives in Wyoming, is concerned about the US rules of engagement – saying, for example, that he had learned the helicopter that shot Welayat Khan as he attempted to flee had to request authorization to fire, even though Khan had just killed his son and Birdwell.

His mother is deeply concerned about the insider threat itself, saying that her son’s Army friends in Afghanistan are afraid of some of the Afghans they serve with.

“They’re training with these Afghan people and they’re doing their thing and they know it’s wrong,” she said. “They know who they can trust. They know who they can’t trust. They are in fear. Every day.”

Some analysts see Nato’s decision last week to scale back some joint operations as a worrying sign.

Nora Bensahel at the Center for a New American Security think tank said it raised serious questions about the US strategy in Afghanistan. “This will create a vicious cycle, where an emboldened Taliban increases its threats against any future joint patrols in order to make this temporary suspension permanent,” Bensahel wrote.

Other critics of the war, including in Congress, have seized upon the insider attacks as an additional reason to accelerate the American withdrawal from the country.

Still, the Afghan conflict is not a top issue in the US presidential election campaign and the insider attacks have not yet sparked widespread national outrage.

Mabry Anders’ home town of Baker City, Oregon appears to have been largely untouched by the war until his death. His hometown newspaper noted in an editorial that Anders’ killing had “erased our collective complacency” about the 11-year-old Afghan war.

The newspaper, the Baker City Herald, estimated that some 2,000 people turned out on the streets for Anders’ funeral procession. Hundreds held tiny flags.

Anders was just 10 years old at the time of the Sept. 11, 2001 attacks, and he enlisted in the Army shortly after graduating from high school. He posted lots of photos on Facebook – many showing his sense of humour, even in Afghanistan.

On the day of his service, the Herald wrote a touching article called “A Hero Comes Home,” noting the different ways people in the community paid tribute to Anders. Among them was a story about a man who went to a bar after the procession and bought a shot for Anders. He left it untouched, along with a handwritten note.

“It said: ‘Mabry Anders, thank you, all gave some and some gave all,’” bartender Sarah Heiner told Reuters. She kept the shot until it evaporated, days later.