Police have released CCTV footage of the stabbing of 15-year-old Alan Cartwright.
The teen was cycling along Caledonian Road, in Islington with his friends they were attacked and he was knifed to death on the evening of 27 February.
The shocking footage sees the suspect immediately stabbing the Holloway School pupil in the chest as comes down the road. Alan managed to continue riding a little while before he collapsed near the junction of Twyford Street.
Another two people can be seen on the video pulling Alan's friends off their bikes. The killer then leaves the scene with one of his accomplices on the back of one of the stolen bikes down Caledonian Road.
A post-mortem examination on 2 March gave the cause of death to be a single stab wound to the chest.
Detective Chief Inspector Chris Jones, who is leading the investigation for the Homicide and Major Crime Command at Met Police, 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."
Police are still appealing for anyone with information about the murder and robbery of the two bikes to come forward. The bikes stolen were a red 'Specialized Hard Rock' mountain bike and a 'Specialized Vita' pedal cycle.
The suspects were wearing dark hooded tops and had their faces partly covered.
Police are asking anyone with information to call the incident room on 0208 345 3734 or contact Crimestoppers anonymously on 0800 555 111 or via crimestoppers-uk.org.