olice are probing the background of a man suspected of killing an officer in a south London custody suite before turning the gun on himself while in handcuffs.
Sergeant Matiu Ratana, 54, died in hospital after the handcuffed 23-year-old opened fire at his chest in Croydon custody centre at around 2.15am on Friday.
The suspect, who had been arrested for possession of Class B drugs with intent to supply and possession of ammunition, also shot himself and remains critical but stable in hospital.
No police firearms were fired and the case is not being treated as terror-related, Scotland Yard said.
It is understood the suspect was not regarded as a subject of interest by security services, but he was reportedly on their radar and had been referred to the anti-extremism Prevent programme.
A murder probe has been launched with the Metropolitan Police investigation expected to focus on the motive for the killing.
The Independent Office for Police Conduct (IOPC) is assessing how it was allowed to happen. Investigators attended the scene, obtained CCTV and body-cam footage and are taking initial accounts from the officers present.
The IOPC said the suspect was taken into the building and sat in a holding area in the custody suite, then opened fire while still in handcuffs as officers prepared to search him with a metal detector.
IOPC regional director Sal Naseem said: “It is at that point that shots were fired resulting in the fatal injuries to the officer and critical injuries to the man.
“A non-police issue firearm, which appears to be a revolver, has been recovered from the scene. Further ballistic work will be required.”
Known as Matt to his family and friends, Sgt Ratana, originally from New Zealand, joined the force in 1991.
Met Commissioner Dame Cressida Dick, who with the Mayor of London, Sadiq Khan, led police officers across the capital in a minute’s silence on Friday, described Sgt Ratana as a “talented police officer”.
He was “big in stature, big in heart, friendly, capable, a lovely man and highly respected by his colleagues”, and leaves behind a partner and adult son, Dame Cressida said.
Forensic officers in white suits were seen entering the police station on Friday morning, while floral tributes were left throughout the day.
Forces across the country flew flags at half-mast as a mark of respect and tributes poured in for Sgt Ratana, who Dame Cressida Dick described as a “lovely, lovely, much-respected police officer”.
New Zealand prime minister Jacinda Ardern told the officer’s family “we share your sorrow and have all our condolences”. UK Prime Minister Boris Johnson offered his “deepest condolences”.
Sgt Ratana is the eighth police officer in the UK to be shot dead in the last 20 years and the first to be murdered by a firearm in the line of duty since Pcs Fiona Bone, 32, and Nicola Hughes, 23, in September 2012.
They were murdered by Dale Cregan in a gun and grenade attack while responding to a report of a burglary in Greater Manchester.