Officers were called to reports of a child being assaulted in High Street just before 1.30am today (February 16).
After gaining entry to a property, officers found a man who was experiencing a medical emergency.
Police say he was very agitated while actively resisting against officers.
He was restrained shortly after.
London Ambulance Service attended and he was transported to an ambulance where he became seriously unwell.
He was taken to hospital for treatment where was pronounced dead.
His next of kin have since been informed.
The Met’s Directorate of Professional Standards is aware and a referral has been made to the Independent Office for Police Conduct (IOPC).
A referral in these circumstances is not an indication that officers are believed to have done anything wrong.
It is a mandatory step when anyone dies or suffers serious injury following contact with the police or while in their custody.
T/Commander Andy Brittain, who is overseeing the response to this incident, said: “Our thoughts are with the family of the man who has died. We will ensure they are fully supported.
“I know the community in South Norwood will want to be reassured that the incident was handled appropriately.
“The IOPC is conducting an investigation to provide that independent scrutiny.
“We must also acknowledge the impact that incidents like this have on the officers involved.
“In this case they were responding to an emergency call involving a child in danger and on arrival at the scene, were met with a very challenging situation.
“No officer ever wants to be involved in an incident where someone loses their life and we will ensure they get all the support they need.”