As shooting began on Bloody Sunday, the revving of army engines and the shouting of soldiers and civilians made the moment sound "like Judgment Day", a witness said yesterday.
Mr Eunan O'Donnell, a Derry teacher, said the high-velocity shots made a "merciless sound".
He added: "At the time I didn't believe the army would be firing live bullets at men, women and children . . . I assumed the soldiers were either firing over the heads of the crowd to disperse them, or firing blanks to scare the crowd."
Mr O'Donnell, who said he was almost certain the first volley of shots he heard in Rossville Street came from the city walls, described the advance of Saracen armoured personnel vehicles on the crowd of civil rights marchers.
Replying to Mr Arthur Harvey QC, for next-of-kin of the victims, he agreed he had the impression that the engines were being revved deliberately to create fear. The army vehicles "looked like they were obviously on the attack".
He saw soldiers behind the Saracens, in firing positions and shouting and roaring. He agreed it sounded like "battle cries".
He and a companion ran into alleyways. "Hundreds of people ran as we did; there was genuine panic at the sound of the volley of shots and the sight of the soldiers. I was really scared and people were shouting: `That's live rounds.'
Another teacher, now retired, Ms Kathleen Turner, described hearing a single rifle shot while in William Street before entering the Bogside. She saw a boy on the road with his arms in the air in a V-shape, and several men rushed over to him when he fell. She had not seen any weapon in the boy's hands.
With her sister and others she ran through waste ground to Rossville Street, where she saw Saracens enter the street.
"The soldiers were shooting live ammunition. The sound of the shots was absolutely terrifying," she said.
She thought at the same time that she heard shots coming from the city walls area. "I recall feeling trapped. I just fled."
Mr Tony McCourt also said he heard a shot while in William Street and, looking in the direction of the shot, he saw soldiers near the GPO sorting office but none was pointing a gun at the crowd. He then heard a second shot in the same area.
Mr Billy McCartney said he had joined in stone-throwing by a group of youths at soldiers in a derelict building off William Street. The soldiers retaliated with rubber bullets. Then a live shot rang out, and a boy he knew to be Damien Donaghy fell to the ground clutching his leg.
Within a few seconds another live shot rang out and hit an elderly man, Mr John Johnston. At the time, he formed the view that the two shots had been fired by two soldiers on the flat roof of the Presbyterian church north of William Street.
The inquiry continues on Monday.