There is a news report about the incident here, which includes a recording of the ruckus:
The reporter expresses his surprise at the calm response of the Sinn Féin delegates. I think some context would probably explain that:
The speaker, Alex Maskey, joined the Provisional IRA at the outbreak of The Troubles in 1969. He was a barman and amateur boxer (losing only four times in 75 fights).
Maskey was interned twice in the 1970s and went on in 1983 to become the first Sinn Féin member to sit on Belfast City Council during the troubles. Whatever you think of his politics, being a lone voice on the council and a very public member of Sinn Féin at that time must have taken some balls. Indeed Alex Maskey survived nine genuine assassination attempts, which puts Pierre Royan’s starter pistol into perspective.
Cllr Maskey became Lord Mayor of Belfast in 2002 and was involved with brokering the ETA ceasefire in the Basque region in 2006. He remains active in politics, having recently commented on austerity and the rise of food banks.
Pierre Royan’s political career looks rather more subdued in comparison. He was elected as a Liberal councillor in Hackney’s Moorfields ward in May 1986, followed by the incident with the starting pistol in October of that year.
According to Wikipedia a by-election was held in March 1987 in Moorfields ward because of Royan’s disqualification as a councillor. I’m not sure if discharging a weapon in the council chamber was the cause of this disqualification, but it doesn’t seem unfair to speculate that it might have been…