The Independent Office for Police Conduct (IOPC) is now investigating the incident and the Met's Directorate of Professional Standards is aware, according to the force.
A referral in these circumstances is a mandatory step when anyone dies or suffers serious injury following contact with the police or while in their custody, the force said.
"I know the community in South Norwood will want to be reassured that the incident was handled appropriately," said Commander Brittain.
An investigation has been launched after a man died when officers were called to reports of a child being assaulted.
Metropolitan Police officers were called to High Street, South Norwood, at 1.27am on Sunday.
