A protected witness, Russell Warren, broke down and wept as he described the murder of journalist Veronica Guerin to the Special Criminal Court.
Under cross-examination, he told the court: "I only drove the woman to her death. I only sent the woman to her death."
The court adjourned for five minutes to allow Warren to compose himself. When he returned to the witness-box, he told the three judges: "I am very sorry about that."
Cross-examined by Mr Terence McDonald QC, counsel for murder accused Mr John Gilligan, Warren said that after stopping behind Ms Guerin's car at traffic lights on the Naas Road he saw the pillion passenger on a motorbike fire five shots into her car. He said the gunman placed the small handgun in the back of his trousers and the bike swerved off.
Asked how he felt after seeing this, Warren replied: "I was shocked. My stomach was in bits. I just wanted to get out."
He said he thought he opened the door of his van but did not get out. He told Mr McDonald that he "probably" wanted to help Ms Guerin as a number of other people did. "Something just clicked in my head and I said I better get out of here. It felt like ages. Everything was in slow motion." Asked what had clicked in his head, Warren replied: "I realised what I was after doing, after helping to murder somebody."
Warren said he drove up a slip road and through Clondalkin and then back to the M50. He then phoned Mr Gilligan. He went home and had a shower and later met a friend and went for a drink to a pub in Rathgar where they watched football and placed bets.
He said when he was in the pub somebody came in with a newspaper which had news of the killing and he also thought it was on the television. Asked if anyone would have known he had just witnessed "the ultimate nightmare", Warren replied: "I don't think they would. I wasn't really speaking to people."
Warren said he gave the blue Lite Ace van which he was driving that day to a friend and told him he would continue with the lease payments but he did not. "I just didn't want the van."
It was the 15th day of the trial of Mr Gilligan (48), who has pleaded not guilty to the murder of Sunday Independent crime reporter Ms Guerin (37) at Naas Road, Clondalkin, Dublin, on June 26th, 1996.
Mr Gilligan also denies 15 other charges alleging the importation of cannabis and firearms and ammunition offences.
The prosecution claims Mr Gilligan was "in control and command" of a criminal gang which imported and distributed large amounts of cannabis and that he organised the murder of Ms Guerin.
Warren admitted under cross-examination that gardai had found some cannabis during a search of his house in 1997, but he said no heroin had been found. He admitted he had never been interviewed about the cannabis.
The trial continues today.