The family of a 15-year-old passionate cyclist stabbed to death in a "senseless" street attack broke down in tears today as they appealed for witnesses to come forward.
Alan Cartwright managed to continue cycling a short distance after the attack on Caledonian Road in Islington, north London, on Friday, but soon collapsed and was pronounced dead at the scene later.
Police have released "shocking" CCTV footage showing the moment the teenager was stabbed in the chest as he was cycling with friends along a busy road.
Alan's mother and sister described the Army cadet and Celtic and Arsenal fan as a "joker" who loved bikes and never caused any trouble.
Fighting back tears, Alan's mother Michelle Watson, 39, said: "He always made you laugh about anything and everything. He was just the funny one out of his friends.
"I feel angry, I want somebody found for this. I just feel numb.
"Looking at the CCTV footage it looks like he got punched, like somebody had just hit him.
"It was so quick, he just carried on riding and two minutes up the road he is collapsed and dead. It's like it's not real.
"I would say to witnesses, if you've got any sort of conscience come forward because a brother and son is dead."
The teenager's sister, Cherrie Smith, 21, broke down when she spoke of him not being there when she gets married.
Ms Smith said that her brother's death has not fully sunken in yet because the family have not seen Alan's body.
She said: "We want any witnesses to give as much information as they possibly can. If you have a little brother or sister, ask yourself 'what if it was them?'
"If that was me, I wouldn't be able to live with myself.
"People are saying 'wrong place, wrong time', but those people shouldn't be carrying knives on them. The whole of his life Alan has grown up in the Cally (Caledonian Road) and you just don't expect it.
"He has always put a front on in front of me and his friends that he was like a hard man, but he wouldn't hurt a fly, he really wouldn't.
"I just clearly hope someone gets found for this - knowing he has been taken away from us in such an unlawful way, it's just heartbreaking because there's a chance someone could get away with this.
"We clearly think it was a bike robbery, but the question is 'why'? Why has that person done that?"
In the CCTV footage, a second suspect is shown lunging at one of the Alan's friends and knocking him off his bike.
A third is seen crossing the road and grabbing another friend to pull him off his bike.
A post-mortem examination yesterday concluded that the cause of Alan's death was a single stab wound to the chest.
Detective chief inspector Chris Jones, who is leading the investigation for the Homicide and Major Crime Command, appealed for help in identifying the three suspects.
DCI Jones said that, while he was keeping an open mind, lines of inquiry suggested that the motive may have been theft.
He also made it clear that Alan was not a gang member.
"Alan, in my mind, was not a gang member and was purely a 15-year-old boy cycling with his friends on a Friday night at 7.30pm," he said.
" The footage of the suspects attacking Alan and his friends is truly shocking. Alan stood no chance of defending himself against his attacker, who casually stepped out in front of him and stabbed him in the chest.
"Identifying and arresting the suspects is our absolute priority. We are working tirelessly and the investigation is moving at a fast pace.
"It is obvious from the footage that Caledonian Road is busy with cars and pedestrians. We have already spoken to a number of witnesses who have provided helpful information to the investigation; however, I would like to re-appeal to anyone who may know something about Alan's murder and the robbery of the bikes.
"Where are the two bicycles that were taken? Someone may have noticed a new bike brought home or perhaps you have been offered a similar bike for sale? If so, I would urge you to contact the police.
"I would like to reassure anyone who is worried about contacting the police that they will be treated with the utmost sensitivity."
All three suspects are described by police as male youths who were wearing dark tops and had their faces partly covered.
The bicycles stolen during the stabbing were a red mountain bike and a black and red pedal cycle.