The 23-year-old was hit by a bullet and remains in critical condition under police guard in hospital.
Sources say there was “zero chance” he was well enough today to speak to officers keen to find out how he had a gun in the police custody suite in Croydon, South London.
Cops also remain baffled at how he fired the fatal shot that hit Sgt Ratana with his hands cuffed behind his back.
Sources suggest the gun’s barrel may have been concealed in an intimate place inside his pants.
The suspect is said to be autistic and of Sri Lankan heritage.
Cops today swooped on four locations linked to him including a house in nearby Norbury.
The home belongs to Channa de Zoysa and wife Elizabeth, who live there with their five kids, including son Louis, 23.
One neighbour said the 23-year-old was “very awkward and kept himself to himself”.
“The police have been outside the address since yesterday morning,” another neighbour said.
“All we know is that it’s connected to the incident in Croydon.”
Forensics are checking the gun, while CCTV and bodycams are also being examined.
Traumatised cops who survived the shooting will be quizzed once mentally fit.
Investigators were also looking into possible motives of the suspect – but cops have insisted it is not a terror probe.
Police searches are taking place at four locations – the custody suite, the site where he was arrested, and two addresses including the one pictured.
He was referred to the Prevent anti-terror scheme in 2018 over alleged Islamist and right-wing views.
Deputy assistant commissioner Stuart Cundy said investigators have CCTV from the custody suite and bodyworn video from the officers.
Mr Cundy said: “I would reiterate this is a murder investigation not a counter-terror one.”
He added: “We have recovered the gun from the custody suite where Matt was shot and that gun is being forensically examined.
“We also have CCTV from that custody suite which shows the events, and we have body-worn video of our police officers who were involved in the circumstances surrounding the arrest of the suspect.”
Police said forensic searches at all four locations will be “rigorous” and are expected to take days to be completed.
Mr Cundy said Friday was a “dark and sad day for the police family” and offered his thoughts to Sgt Ratana’s partner, family and colleagues.
He added: “Everyone working on this investigation, from the forensic specialists to the local officers holding the cordons, does so with a heavy heart but a determination to find justice for our colleague and his family.”
The suspect had been detained in an area of London Road, Pollards Hill for possession of ammunition and possession of class B drugs.
He was taken to the custody centre in Windmill Lane where he remained handcuffed until a door was opened for him to be searched with a metal detector.
“The sergeant opened the door to admit him and take his temperature to comply with Covid rules. But the suspect shot him at point-blank range, ” a source said.
They added: “It would appear the suspect has somehow managed to conceal the gun on his body.”
“However, there are rules preventing any intimate body searches on the street. It can only be done when a suspect is booked into a custody suite.
The gunman blazed off more shots, five in all, in a fierce struggle in the corridor at 2.15am.
One hit himself in the neck, leaving him critical and under armed guard in hospital last night.
Desperate colleagues battled to save the stricken officer’s life.
Medics performed open heart surgery on Sgt Ratana at the custody centre.
He was airlifted to hospital but later pronounced dead.
The 54-year-old dad was just months from retirement – and it was revealed he had moved to work in custody as it was safer, as he neared retirement.
He had told colleagues he intended to quit as early as next year, and posted of his excitement at the prospect of “a long healthy life”.