George Verrier was treated by officers who were called to an altercation involving about 20 people in Bromley in the early hours of Sunday.
He did not want to be taken to hospital, said police, but was found unconscious several hours later in nearby Ferndale. He died in hospital.
A 17-year-old arrested on suspicion of murder has been released on bail.
The Met said it had voluntarily referred the actions of officers who went to the scene to the Independent Police Complaints Commission (IPCC) for assessment.
A Metropolitan Police spokesman said: "At this early stage it appears the victim suffered a head injury as a result of the altercation.
"Inquiries continue to establish the full circumstances of the incident."
George, a trainee electrician, was injured in Southborough Road at about 00:45 BST, while on his way home from the party in adjacent Blenheim Road.
Police were called at about 09:30 BST to a home in Ferndale - about a mile away - after he fell unconscious.
He was taken by air ambulance to hospital where he died at about 18:00 BST.
He had been due to have his first driving lesson on Tuesday.
Cornelius Moran, whose 16-year-old daughter was having the party, said: "He was a good friend of my daughter's. A lovely boy from what she tells me.
"My thoughts are with the family."
A woman who lives near the party venue, but did not wish to be named, said: "It looked like a very well-organised party - it was noisy, that's all.
"The family who had the party are such a nice family."
Another neighbour said some partygoers had been turned away from the house.
He said: "We were very much aware of the noise. That stopped at about 12.30am when the music stopped.
"My wife was looking out of the window and she could see three large adults leading a group of youngsters up the road, turning them away from the party."
A 17-year-old boy has died of head injuries following a fight after a party in south-east London.