Detectives have appealed to hundreds of young people who were at a crowded ice rink when a teenager was shot dead to get in contact with them.
Police do not know if James was the intended target
James Andre Smartt-Ford, 16, was shot twice on Saturday night at Streatham Ice Arena in south-west London.
Police said the shooting took place near to the venue entrance, but James managed to stagger onto the ice. He was taken to hospital but pronounced dead.
Six male youths and an 18-year-old man were arrested and bailed.
They will all return to a south London police station at a later date.
Eyewitness John Fitzmaurice, of the Streatham Ice Hockey Club, said a large number of young people entered the rink shortly before the shooting.
"Some young people obtained entrance to the rink then... a fairly large number of people came into the rink illegally through side entrances and proceeded to cause a disturbance.
"I gather some robbery took place then there was an affray and it resulted in a young male being shot."
Police said James was approached at about 2300 GMT by a gunman who fired two or three shots.
"Despite being fatally injured, James managed to stagger a few metres onto the ice, before collapsing," said Det Supt Gary Richardson, of the Metropolitan Police.
Mr Richardson said about 300 young people in their late teens and early 20s were at the rink when the shooting took place.
He appealed for everyone who was at the ice rink disco to contact Operation Trident, the Scotland Yard unit that specialises in investigating black gun crime.
Mr Richardson said the disco was dark at the time of the shooting and security staff patrolled the area with torches.
He said the victim's family were "devastated".
"We are still trying to build up a picture of how James came to be here," he added.
"Did the gunman target a gang of individuals, him on his own or indeed was it that he was not the intended target?"
Tributes to James have been left on the website gonetoosoon.co.uk including one from a "best mate" of Jessie James who was shot dead as he cycled through a Manchester park.
A memorial service attended by more than 100 mourners was held at the United Reformed Church, next to the ice rink, on Monday evening.
Most of those attending were teenagers.
The rink remained cordoned off by police as mourners placed bouquets of flowers outside.