Alan Cartwright from Islington was out cycling
with friends when he was attacked
A man has been arrested on suspicion of the murder of a 15-year-old who was fatally stabbed while riding a bicycle with his friends.
The 18-year-old is being held in connection with the killing Alan Cartwright, on Friday.
CCTV footage of the moment Alan was stabbed in Islington, north London, was released by police on Tuesday.
His family had appealed for witnesses to come forward after he died in what was described as a "senseless" attack.
The suspect was arrested in the early hours after he went to a north London police station.
I feel angry'
The video footage shows Alan and his two friends being attacked and pushed off their bikes by three youths.
He managed to cycle away but collapsed on nearby Caledonian Road and was pronounced dead at the scene.
His mother Michelle Watson said the footage looks like he got punched, yet two minutes later he collapsed and died.
The 39-year-old added: "I feel angry, I want somebody found for this. I just feel numb."
A youth stepped out in front of Alan and stabbed him while he was on his bike
Det Ch Insp Chris Jones 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."
After Alan's two friends were pushed off, the suspects - initially described as men in the hours after the killing - rode off on their bicycles.
Tributes, including a bike painted white, have been left at the place where Alan Cartwright died
A post-mortem examination confirmed the cause of Alan's death as a single stab wound to the chest.
Det Ch Insp Jones added: "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."