A 16-year-old youth who watched civilians suffer appalling injuries and die in front of him was left with a profound revulsion against violence, the inquiry heard.
Mr Hugh Barbour told how for years after Bloody Sunday he tried to block all memories of what he had seen, including the image of Barney McGuigan being cut down by a bullet through the head only a few yards from him.
"I have found it very difficult coming to terms with what I experienced then, but I want to make a statement now so that I can lay to rest memories that I have," he said.
"I think, with hindsight, it was a positive experience for me as it made me see the reality of the Troubles. I had witnessed what one person could do to another when I saw Barney McGuigan, and I knew that I could never justify doing this to another human being.
"I saw reality that day. If I had been a hundred yards up Rossville Street and had not seen Barney McGuigan being shot, I would have joined the IRA."
Mr Barbour, now aged 45, described how as a youth he had been excited at first seeing the soldiers advance. He was anticipating "the usual confrontation" and "expecting to see some excitement".
As events rapidly unfolded, he watched with growing shock the shooting of Michael Bradley and Michael Bridge, the mortally wounded Hugh Gilmore, and - finally and most vividly - the killing of Barney McGuigan.
The witness said he had a very clear recollection of Mr McGuigan standing in the gap between two blocks of Rossville Flats, waving his arms. "I think he was holding and waving a white handkerchief. . . He was shouting "Please, please help - don't shoot me". He was showing himself in clear view and was not trying to hide," said Mr Barbour.
It then seemed to him that Mr McGuigan was shot in the face, and the next clear recollection he had was of Mr McGuigan lying on his back on the ground and his body shaking. "He was in his death throes . . . I can particularly remember seeing the blood spurting from his cheek each time his heart beat," said the witness.
Before that, from a balcony of the flats, Mr Barbour said he had watched a soldier aiming towards the crowd in the car park and firing from the hip. "I was obviously shocked by this, as was everyone else I could see . . . It seemed as if none of us could believe that (he) was actually firing live rounds at the crowd," he said.
"It was the lackadaisical attitude of the soldier that triggered my disbelief. As he fired I noticed someone who seemed to stagger and fall . . . (we) realised that these were live rounds being fired."
After this the mood of the crowd turned from disbelief to anger, he said. "Everyone was shouting and screaming at the soldiers about the shooting. I could see that one man in particular was extremely angry. His name was Mickey Bridge."
Mr Bridge was furious and was "full of adrenalin", said the witness. He had a piece of wood and he "made a go" for the soldiers. Then he was shot by one of them. "It was an amazing thing to see," said the witness. "He was shot and still kept going . . . Several people grabbed him but . . . he broke away from them two or three times. He had to be physically dragged away."
He described how, soon afterwards, as intense shooting continued, he was sheltering with others at the gable end of the flats when several people went out to try to drag the wounded Hugh Gilmore in. Firing was still heavy and it took two or three attempts before they managed it. "I remember thinking how incredibly brave they were, and as well as feeling terribly afraid, I felt ashamed that I didn't have the courage to go and help them."
He said that during all this he had no sense of time. "It felt like forever to me. What happened in that place, on that day, will forever be my personal hell. I had no sense of time at all. I felt powerless."