Former members of the Official IRA, a long defunct republican military group, have been giving evidence to the Bloody Sunday Tribunal.
Giving his evidence in public view at the Guildhall in Derry, OIRA2 - one of eight Officials set to testify - said they had been taken by surprise by the actions of the British Army, on January 30th, 1972, when 14 unarmed civilians were shot dead during a civil rights march.
``We didn't expect an onslaught from the Parachute Regiment.
``We expected that the [British] Army would try and deal with it in the way they would normally deal with what they would consider to be in their opinion an illegal march.''
In the days leading up to Bloody Sunday, the Official IRA had met to decide not to attack troops on the day, he told the Inquiry.
``The command staff took a decision that there would be no activity on the day of the march and this was obviously passed down the line of the chain of command.''
The policy, which had been in place from the introduction of internment in August 1971, stated that members could only open fire in response to soldiers firing live rounds.
The local command held a meeting in the run-up to the march to call for a no first strike ``to reinforce and make sure that everybody understood what the orders of the organisation were.''
In his evidence today, the first member of the Officials to give evidence to the Tribunal - said he and another Official IRA Volunteer, known as OIRA1, had gone to an arms dump at Columbcille Court in the Bogside to collect a rifle, but denied it was with the aim of mounting an attack.
While they were retrieving the gun he said they heard a noisy confrontation involving a 30 to 40 strong crowd.
``Just then I heard someone in the crowd shouting `two boys have been shot!'`` he added.
``Hearing the shouting from the crowd, I automatically assumed that shots had been fired, that first strike had happened and that the Army had engaged in the first strike.''
He was with his associate, OIRA1, when he fired a single round at a soldier on the roof of a Presbyterian Church.
He described the attack as a reflex action: ``Anybody who had planned a snipe from that position would have literally been taking his life in his hands.''