Pte McCollum was last seen at a chip shop in the city at 2.30am. His murder was the IRA's first act of terrorism since the Government replied on Thursday to Sinn Fein's 20 questions about the Downing Street Declaration.
Last March his brother Nigel, 25, was killed in a rocket attack as he carried out maintenance work at a security force base at Keady, Co Armagh. Ten years ago their grandmother, Lily McCollum, was killed by a booby trap bomb said to have been meant for her brother, at that time a member of the security forces.
Sir Patrick reacted angrily to the latest killing. 'The IRA have killed again, this time after interrogating their victim,' he said. 'Is Mr Adams, who calls for peace, now going to condemn these crimes? The IRA besmirch all they touch in the cause of Irish nationalism, just as the Ulster Volunteer Force and Ulster Freedom Fighters and their like besmirch the cause of Unionism.'
Seamus Mallon, the SDLP deputy leader and MP for Newry and Armagh, condemned Pte McCollum's murder which he described as 'mindless and sectarian'.
A few miles from the murder scene, the funeral of Catholic teenager Shane McArdle took place after he and a college friend were killed on Wednesday by Loyalist terrorists in an Armagh taxi office.
Hundreds of mourners, including students and staff at the Armagh College of Further Education, gathered for his funeral. Among them was a taxi driver injured in the attack. Shane, 17, died 24 hours after the shooting. His friend Gavin McShane, also 17, died instantly and was buried on Friday.
Just hours after the funeral the IRA held out the prospect of an end to the tit-for-tat sectarian killing war being waged by Republican and Loyalist groups.
There was no mention of a ceasefire, but the IRA leadership said if Loyalist groups stopped attacking nationalists they would review their position on attacks on those they considered to be responsible.
A statement issued yesterday by the IRA leadership in Dublin said there were some indications the Loyalist groups may be contemplating a halt in their attacks on nationalists.
'The IRA wish to note that any such halt in murderous attacks against nationalists would be a welcome development.
'Should those currently waging and directing the pro- British terror campaign desist from their activity, then as a consequence we in the IRA would monitor the situation and review our position on those responsible for this murder campaign.'
Violence in Ulster has intensified following a wave of sectarian attacks in recent weeks. On Friday night Loyalists in Belfast went on the rampage, police officers were shot at and petrol bombs thrown. The RUC said shots were fired at police in several areas of north and west Belfast. Officers came under automatic gunfire in Sandy Row, near the city centre, and shots were fired in Ballysillan. There were also reports of police coming under attack by petrol bombers in the Loyalist Shankill Road area.
A bus was hijacked in the Donegall Road but later recovered by police, who made two arrests and found a handgun. An RUC spokesman confirmed that two people were being questioned last night.
The violence is believed to be linked to a series of arrests on Monday when RUC detectives investigating the recent upsurge in Loyalist attacks arrested 20 suspects.
Last Friday John Adair, 30, from Hazelfield Street, off Belfast's Shankill Road, appeared in court accused of directing acts of terror by the outlawed Protestant paramilitary organisation, the Ulster Freedom Fighters. It was the first time the charge had ever been used by police in Northern Ireland. Adair was remanded in custody until 3 June.
Hours before the riots erupted, the head of the Anglican Church in Northern Ireland, Archbishop Robin Eames, had warned of unrest. He told an international conference in Armagh that Protestants felt increasingly that violence appeared to work in achieving terrorist ends. He said: 'The question which I fear is now being asked by many is this - does violence, the support of violence or an ambivalent attitude to violence, actually pay off? This troubles me greatly.'
Three-year-old IRA bomb victim Emma Anthony, three, who has been critically ill in a coma since being injured in an IRA bombing which killed her father over a week ago, woke from her coma yesterday and demanded her mother.
Hospital spokesman Gerry Carson said all staff were delighted by the improvement: 'It's amazing, her condition has changed. She is off the ventilator, she has improved and is described as stable. One of the first things she said was 'I want my mummy'.'
Irish government and Northern Ireland Office representatives will travel to the border tomorrow for an event of unusual significance: the opening of a new waterway linking the lakes of Fermanagh in the North with the Shannon river system in the South.
For security reasons, precise details of the formal ceremonies and the identities of those planning to attend them are being withheld until almost the last minute. But to mark the opening of the Erne-Shannon waterway, one of the longest in Europe, a Northern Ireland ceremony will be held at Corraquil Quay, on the Woodford River (one of the connecting links), followed by a similar event south of the border, probably at Ballyconnell.
Trobled border, Review