A former soldier has described watching a terrorist gunman stand over his stricken comrade and riddle his body with bullets during an attack which left two soldiers, including one from Birmingham, dead.

Mark Fitzpatrick was badly injured in the Real IRA attack outside Massereene Army Barracks in Northern Ireland that claimed the lives of his fellow Royal Engineer sappers Mark Quinsey, from Highters Heath, Birmingham, and Patrick Azimkar, of London, in March 2009.

Giving evidence at Antrim Crown Court in the trial of two men accused of the murders, Mr Fitzpatrick recalled the moment he and five fellow soldiers were fired on as they collected pizzas from two delivery drivers parked outside the gates of the barracks in Antrim town.

"I heard a noise, I don't know what it was, then I heard someone shout 'Get down'," he said.

"As that happened Pat (Azimkar) fell on top of me, I hit the floor and crawled round the car, I looked up and saw a gunman in a balaclava shooting my friend."

Sappers Azimkar, 21, from London, and Quinsey, 23, from Birmingham, both died at the scene of the ambush.

High-profile republican Colin Duffy, 43, from Forest Glade in Lurgan, Co Armagh, and Brian Shivers, 46, from Sperrin Mews in Magherafelt, Co Londonderry, deny charges of murder and the attempted murder of six other men.

Mr Fitzpatrick sustained gunshot wounds to his hand and shoulder, with one bullet puncturing his lung. His injuries were so severe that he has since left the Army.

The ex-sapper said he looked out through the window of the pizza delivery car he had crawled into and caught the eye of the gunman.

"When he seen me in the car he opened fire," he said. "It was an automatic, probably about 10 to 15 seconds of constant fire."

Mr Fitzpatrick said moments earlier the killer had paused over Sapper Azimkar and shot him again.

"Whoever it was wanted to cause damage and they finished him off before firing in at me," he said.

He added: "There was no remorse. He knew what he was doing, he just seemed to do it all quick."

Relatives of the murdered sappers were visibly upset in the public gallery as Mr Fitzpatrick recounted the incident to a silent courtroom.

Duffy and Shivers showed no emotion from the dock.

While Mr Fitzpatrick said he saw only one gunman, CCTV footage of the shooting played to the court on Monday showed two masked attackers.

Pizza delivery man Anthony Watson was in the vehicle Mr Fitzpatrick crawled into. He was shot in the shoulder and chest.

Earlier the court heard that 63 spent ammunition cartridges and two live ones were found at the scene of the shooting.