THE widow of a soldier who shot a colleague before turning the gun on himself yesterday told an inquest that his irrational behaviour may have been triggered by anti-malaria drugs.

Corporal John Gregory, 30, from Catterick, North Yorkshire, fired up to ten bullets into Sergeant Robert Busutill, 30, while on peacekeeping duties in Afghanistan.

He then turned the assault rifle on himself during a farewell barbecue at a military base at Kabul Airport last August, the hearing was told.

His widow, Annette Gregory, 31, said that his behaviour was caused by anti-malaria drugs.

Cpl Gregory was given the drugs Chloroquine and Proguanil before being posted to Afghanistan.

Mrs Gregory said that her husband had suffered sickness, diarrhoea, sleeping problems and paranoia before he left.

She said that he had interrogated her about her phone calls, changed the password to his e-mails and had become suspicious of her relationship with his younger brother.

She denied claims that Cpl Gregory could not handle his drink and was argumentative, saying they had a happy marriage.

But Army pharmacist, Colonel Graham Stewart, said that while there were side effects to the drugs, psychosis was rare.

He said it was more likely that a combination of alcohol and the drugs could have caused problems.

The inquest heard earlier that Cpl Gregory was found to be two-and-a-half times the legal drink drive limit - his small group having got hold of six crates of lager and a box of wine.

Sergeant Dale Garner who slept in a bed next to Gregory, recalled how the soldier had become aggressive after drinking three nights before the fatal incident.

He said that the pair had sat down over a coffee during which Cpl Gregory allegedly said: ''I want to punch your lights in.''

He told the Chippenham inquest how he was woken by gunfire on the night of the barbecue.

He arrived to find the bodies of Cpl Gregory and Sgt Busuttil, of Swansea.

The court earlier heard how Cpl Gregory and Sgt Busuttil had come to blows after banter got out of hand, but had made up.

It was said that Cpl Gregory returned half an hour later with his loaded SA-80 rifle and began firing.

The two soldiers, both of the Royal Logistics Corps, based at the Marne Barracks in Catterick, were part of a small contingent from the British Army in the International Security Assistance Force.

The case resumes today.