The prime suspect for the killing of Sergeant Matt Ratana has been formally arrested on suspicion of murder, with detectives now waiting to question him under criminal caution. Louis de Zoysa, 23, had been too ill to be arrested after the incident, having received gunshot wounds, which are believed to have been self-inflicted. Ratana, 54, died after being shot in the custody suite at Croydon police station by a suspect who had his hands handcuffed behind his back. The killing on 25 September stunned police officers. Ratana died from a single gun shot to the chest. The suspect, who has been in hospital ever since, had been too ill to be arrested and had been under guard. On Friday the Met said that after seven weeks of medical treatment and recuperation, the suspect had been medically assessed to be fit enough to be arrested. In a statement, the Met said: “The man’s condition, originally critical, has since stabilised and is no longer considered life-threatening. “Therefore, on Friday 13 November he was considered fit to be arrested on suspicion of murder. “However, as the man remains in hospital, officers will liaise with the relevant medical and legal teams to make an assessment of when he will be fit for interview.” Det Supt Nick Blackburn last month told an inquest into the death of the officer that the suspect had been stopped by officers on patrol at about 1.30am on Friday 25 September. A search uncovered drugs and ammunition, and he was arrested for being unlawfully in possession of ammunition and for possession of a controlled drug with intent to supply. The suspect was handcuffed with his hands behind his back and taken to the police station. Blackburn said: “Upon arrival, he was taken to a holding room with police officers, where he remained in handcuffs while officers prepared to search him. “The custody sergeant, Matt Ratana, entered the holding room as part of his duties when the suspect produced a firearm and discharged the weapon several times, during which both Police Sergeant Ratana and the suspect were injured. “Police and paramedics treated him at the scene, and he was taken to hospital by the London ambulance service. Tragically, Police Sergeant Ratana’s life was pronounced extinct at 4:10am on Friday 25 September 2020. “A revolver handgun was recovered from the scene.​”​ The Met investigation has involved searches of several scenes, inquiries about the suspect and his history, and reviews of police officers’ body-worn video and CCTV at the custody centre. A funeral for the popular sergeant last month heard glowing tributes from colleagues and friends. Ratana was born in New Zealand, with Māori heritage, and had served as a police officer there and across London. The Met commissioner, Cressida Dick, said he was an inspirational officer: “Matt was a fantastic professional police officer, a brilliant sergeant, a leader, a supremely loyal colleague, and friend … he mentored and coached generations of officers, young and old, junior and senior … as enthusiastic after 25 years as he was after two.” After the service, the former All Blacks’ captain Zinzan Brooke led a haka outside the chapel, along with members of the London-based New Zealand culture group Ngāti Rānana.