A man has been arrested in Norwich in connection with the investigation into the murder of Sergeant Matt Ratana is still being held by police.
The 54-year-old Metropolitan Police officer was shot dead by a handcuffed suspect, widely named as 23-year-old Louis De Zoysa, as he was booked in at a custody suite in Croydon, south London, in the early hours of Friday.
Detectives are yet to speak to the suspect, who remains in a critical condition in hospital after he shot himself as he opened fire with a revolver while handcuffed behind his back.
An early hours raid saw a second suspect arrested at an address in Norwich at 2pm on Sunday, September 27 on suspicion of supplying a firearm.
The Met Police confirmed the man, who has not been identified, remains in custody at a South London police station where he is being questioned.
Croydon Custody Centre, where the shooting took place, remains a crime scene, while searches in London Road, in Pollards Hill, south London - where De Zoysa was arrested - and a location in central London have also been carried out.
The suspect had been arrested for possession of ammunition and possession of class B drugs with intent to supply following a stop and search, before being handcuffed and taken to Croydon Custody Centre.
Police investigating the murder of Sgt Ratana are continuing to search at a house, believed to be the suspect’s family home, in Southbrook Road, Norbury, south-west London.
Searches are also taking place at a property in Surrey which includes several derelict buildings and more than 30 acres of farmland. The “complex” search is expected to take days to complete.
Deputy assistant commissioner Stuart Cundy said: “It is five days since the murder of our colleague and our work continues at a high tempo.
“We have traced a number of witnesses who have been able to contribute significant information about the events leading up to the shooting.
“We continue to pursue multiple lines of inquiry and consider the results of initial forensic examinations, including of the gun recovered from custody.”
No police firearms were discharged in the incident, and the case is not being treated as terror-related.
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