Cpl. Matthew Wilcox is charged in the 2007 shooting death of Cpl. Kevin Megeney at Kandahar Airfield. (Andrew Vaughan/Canadian Press)

One of the first soldiers to come to the aid of a comrade shot in the chest in Afghanistan said Friday he recalled the accused gunman apologizing to the wounded man in their tent on the NATO base in Kandahar.

Master Cpl. Matthew McKay told a military trial in Sydney, N.S., he was off-duty and hanging out with several buddies at the base when they heard a shot on March 6, 2007.

"It sounded like a 9-millimetre. We had a general idea of where it came from." He then heard someone yell, "Oh God! Someone help."

Lt.-Cmdr. Robert Fetterly, the lead prosecution lawyer, is trying to prove that Cpl. Matthew Wilcox, 23, fired the weapon that killed Cpl. Kevin Megeney, 25, and he has argued the apology amounts to an admission of guilt.

The court martial heard Thursday the two off-duty reservists from Nova Scotia were playing a game of quick-draw in their tent when Megeney was fatally shot in the chest.

Wilcox has pleaded not guilty to manslaughter, criminal negligence causing death and negligently performing his duty.

Cpl. Kevin Megeney, 25, was fatally shot in his tent in Afghanistan. (DND/Canadian Press)

McKay said he was the second person into the tent as he and others rushed in to see what had happened. "There was still smoke in the air," he recalled. "You could smell it."

He said he saw Wilcox propping up Megeney on his right side close to the ground. McKay ran out of tent, grabbed a first-aid kit and came back in, talking to the wounded man to try to keep him from lapsing into shock.

McKay was asked if Wilcox said anything.

"Cpl. Wilcox said, 'C'mon Kev. C'mon Kev. I'm sorry," McKay testified.

He was asked to describe Wilcox's demeanour. "He seemed shocked or overwhelmed by what was happening," McKay said.

Fetterly has said the evidence will show Wilcox did not follow proper safety procedures when he carried a loaded 9-millimetre handgun — against military rules — into a tent he shared with Megeney.

The trial continues.