But Oxfordshire Assistant Coroner Alison Thompson said that, although there was no apparent motive for the man opening fire on British troops, killing Sergeant Gareth Thursby, 29, and Private Thomas Wroe, 18, from 3rd Battalion, The Yorkshire Regiment (Duke of Wellington’s), there was no established link between him and the insurgency in Afghanistan.
An inquest at Oxford Coroner’s Court today heard that both men died of multiple gunshot wounds after the man, a member of the Afghan Local Police, opened fire on them at a checkpoint in Helmand Province on September 15 last year.
A third soldier was injured after being shot several times in the incident, which came in a spate of “green-on-blue” attacks - where members of the Afghan security forces turned on their coalition colleagues - in the latter part of 2012.
Recording a verdict of unlawful killing for both men, Ms Thompson said: “It is often difficult if not impossible to establish motivation in this sort of case, making it especially hard for families to come to terms with the death.
“And I am sorry that I am not going to be in a position today to provide a reason for this appalling attack as I have heard no evidence as to why it took place and therefore it would be wrong and improper for me to speculate in any way.”
The inquest heard that the Afghan local policeman was visiting the checkpoint, called Tora, in Nahr-e Saraj, from another one nearby when he opened fire.
He was well-known to the men there, the inquest heard, and was known to be “pro-Isaf (International Security Assistance Force)” and a “champion of the partnership” with the coalition.
The man, known as Gul Agha, had been laughing and joking with soldiers at the checkpoint before he turned his AK-47 on them.
Fellow troops shot him dead and administered emergency first aid but Sgt Thursby, from Skipton, North Yorkshire, and Pte Wroe, from Holmfirth, West Yorkshire, could not be saved.
The inquest heard that Afghan security forces were required to make their weapons “safe” when entering the checkpoint, but did not have to unload or hand them in, and it was not known whether the man had made his safe.
Lieutenant Callum Cameron, platoon commander of 3 Platoon, Alma Company, told the inquest all Afghan Local Police (ALP) visitors were checked and vouched for by colleagues before they were allowed into the checkpoint, and the man in question had been vouched for.
The inquest also heard that, depending on the threat level, soldiers within the checkpoint did not wear their full protective body armour, unless they were manning guard towers.
Lt Cameron admitted it would have been unusual for the man to be allowed to have his weapon - which was slung over his back - in the “welfare area” of the base, but the inquest heard that nobody had challenged him or felt threatened.
“He was very well-known, very identifiable,” he said.
“He was known to be very pro-Isaf. He was a real champion of the partnership.”
Soldiers from 3 Yorks who gave evidence to the inquest described the shock that the man, who was known to them, had turned on them.
They said his behaviour had been no different from normal, and they could think of no reason why he would turn on them.
The inquest heard that the man had a longstanding foot injury after apparently being shot during the Russian invasion of Afghanistan, and had apparently been ill more recently.
He arrived at the checkpoint at 10.30am, and was escorted to the ALP area of the camp.
At around 2.45pm he asked for medical help for his foot but was told - as he had been on previous occasions - that Isaf medics could not help him with primary care issues.
As he sat at a table with the soldiers, he opened fire, injuring one private, killing Pte Wroe who was hit four times, missing two other soldiers, and then killing Sgt Thursby, who was shot five times.
Several of the soldiers told the inquest they had not heard the AK-47 carried by the man being “cocked” before the attack - which would have made a distinctive noise.
But the coroner said the man had had plenty of time between arriving at 10.30am and the incident at 2.45pm to prepare the weapon.
She said: “He was trusted, he was well-known and what happened after that was entirely unpredictable.
“It is not for me to say what should or shouldn’t have been the policy, I simply deal with the factual findings as I see them.
“Essentially this man had every opportunity to make this attack, there is nobody that saw him as a threat and treated him in a way that suggested he might be.”
She said she could not establish why the attack had taken place and the inquest heard an investigation had been carried out by the Royal Military Police’s Special Investigations Branch which found no links to the insurgency, as well as investigations by Afghanistan’s National Directorate of Security (NDS).
Major James Glossop, from the Operational Training and Advisory Group, which looks at what lessons can be learned, said there was a spike of “insider attacks” in Afghanistan in August 2012, but it was impossible to be “100%-proof” from them.
He said less than 50% of incidents were found to be related to the insurgency and in this case there was nothing they would advise should not have been done.
Asked about the rules concerning body armour - which the inquest heard would not have saved the lives of the two men - and weapons inside checkpoints, he said it was difficult to adopt a “blanket approach”.
“You build a relationship, you build that trust and that is extremely important as part of that transition process,” he said.
Giving her verdict, the coroner said it was “impossible to entirely legislate” against the threat of insider attacks, because of the importance of building relations.
She told the families: “I can only hope that by hearing from Gareth and Thomas’s colleagues today at least you know exactly what happened.”
Speaking outside the inquest, Pte Wroe’s father, Michael, said he did not want to point the finger at anyone, and they now knew what had happened to their son and to Sgt Thursby.
“We would like to thank the soldiers for talking today and explaining to us what happened,” he said.
“Just thanks for their help and we hope that lessons can be learned from this.”
The inquest was also attended by the parents of Kingsman Ryan Ward, who shot the Afghan gunman dead, but later killed himself.
An inquest into the 20-year-old’s death previously heard that he was found hanging at his family home the day after Sgt Thursby’s funeral.