It was the first major atrocity of the Troubles coming week's before Bloody Sunday. Parishioners coming from Mass at St Patrick's Church on Donegall Street paid little attention to the men in the car parked close to McGurk's Bar on North Queen Street.
Some people stopped to buy a newspaper from a young boy standing on the pavement outside McGurk's Bar before making their way home.
The eight-year-old became curious about the waiting car, which had a small Union flag sticker on the back windscreen.
As he looked on a man got out of the vehicle and carried a large box over to the door of the bar.
The boy saw the man light something in the box and then run to the car, which sped off in the direction of loyalist York Street.
The boy ran over to the door where he saw sparks coming from the box.
In panic he ran shouting to a man nearby that there was a bomb in the doorway.
Seconds later the pair were lifted off their feet by the force of the blast.
Within seconds McGurk's Bar lay in ruins, torn apart by 40 pounds of explosive.
Fifteen people were dead and a further 16 injured.
Those killed included schoolchildren and pensioners.
All of the customers were from North Queen Street and were regulars at McGurk's – one of the most respected families in the area.
The British army initially claimed that the explosion had been an IRA own goal and that the bomb was being made in the bar when it prematurely exploded.
It was a lie that for many years caused huge pain to the families of those murdered.
Catholic primate Cardinal Conway described it as "a new and vicious twist in this terrible spiral of violence and counter violence".
The McGurk family had lived in the two storeys above the bar.
It was an old building which, when the bomb went off, crumpled like a deck of cards.
In 1996 Patrick McGurk's son John, who was 10 years of age at the time, vividly recalled the explosion that killed his mother and sister.
"It was sometime between 8pm and 8.30pm and I was in the sitting room of our house which would have been the room above the bar.
"If you had put your ear to the floor you could hear the noise from the bar.
"It really wasn't a case of lights going off – it was like something out of a really bad horror film.
"I remember tumbling in air and space amid this massive rush of wind and noise.
"It must have been just a matter of seconds.
"I couldn't remember anything else because I must have been unconscious for a while but I don't know how long it was."
Despite lying trapped beneath a wall of concrete John escaped with just a minor injury.
"It was miraculous for me because a person – Jimmy – who was just a few feet away from me was killed.
"I woke up and I really didn't know what had happened.
"There was then the realisation that the building had collapsed and I was stuck.
"I wasn't physically injured. The only injury I had was an injured finger but that was it."
The 10-year-old lay beneath the wall in darkness, with dust and sediment from the destroyed bar falling onto his face and into his mouth.
He prayed. Then out of the silence he heard voices and people ploughing through the mass of rubble.
He began shouting and soon after there was a voice above him, moving debris.
"It's the tragedy of Northern Ireland that a few years later the man who saved me, a man called O'Hanlon, was picked up by a loyalist murder gang at Carlisle Circus coming back from a chip shop and murdered," John said.
Reliving the nightmare of losing a mother and sister, he said: "The worst thing about it was that I'm nearly sure that I heard my sister crying for help because there wouldn't have been any other young female stuck there.
"It's possible that it was my imagination. It's possible that she was already dead but that's what I remember."
It had been thought that Philomena and Maria McGurk hadn't been in the house at the time.
They usually went to the Saturday vigil Mass in St Patrick's.
But that night they returned just before the bomb exploded.
However, for John McGurk there was comfort in having his father, Patrick, with him on the ambulance journey to Belfast's Royal Victoria Hospital, where doctors examined him and gave him the all-clear.
It wasn't until the following day that he was told about the deaths of his mother and sister.
Expressing admiration for his father's reaction to the bombing and its aftermath, John said: "I remember he went on the television. I know that people can be critical of people going on TV and saying they forgive the people who carried out an atrocity.
"But he was one of the first people to do that and he genuinely meant what he said because he is a decent, Catholic, Christian man."
Only one person was ever convicted for their part in the massacre.
In 1978 Robert James Campbell, a self-confessed UVF man was given 16 life sentences for the bomb attack
When arrested by police, Campbell said: "I have worried about this since and I am glad to be going to jail to get it off my mind."
Those who died in McGurk's Bar
Philomena McGurk (46), Maria McGurk (14), James Cromie (13), John Colton (49), Thomas McLaughlin (55), David Milligan (52), James Smyth (58), Francis Bradley (61), Thomas Kane (49), Kathleen Irvine (53), Philip Garry (75), Edward Kane (29), Edward Keenan (69), Sarah Keenan (58), Robert Spotswood (38).
