The suspect in the fatal shooting of a custody sergeant at Croydon police station on Friday is 23-year-old Louis de Zoysa, sources have told the Guardian. He remains in hospital in a critical condition, the Metropolitan police said on Sunday, after the force’s chief commissioner, Cressida Dick, paid tribute to the fallen officer. A second man has been arrested on suspicion of supplying the revolver used in the fatal incident, and is being held in a south London police station, the force added. Speaking on National Police Memorial Day, Dick said it was “her sad duty” to confirm the death of Matiu (Matt) Ratana, 54, who had spent nearly 30 years working in the force as a uniformed officer in the capital. Originally from Hawke’s Bay, New Zealand, the officer moved to the UK, where he joined the Met in 1991 and served in various roles in the West End, Westminster and Hackney before transferring to Croydon in 2015. “As a colleague, he was big in stature and big-hearted, a friendly, capable police officer. A lovely man, highly respected by officers and staff, and by the public, including suspects he arrested or dealt with in custody,” the Met commissioner said. Ratana was killed inside a custody suite on Friday. According to watchdog the Independent Office for Police Conduct (IOPC), the suspect, 23, had his hands cuffed behind his back but was nevertheless still in possession of a loaded revolver, which he used to shoot the officer and then himself. The custody officer died in hospital. Dick said the suspect is “in a critical but stable condition”. He has not yet been questioned, the Met added in an early afternoon update. The suspect is thought to have been arrested by local officers for possession of ammunition and possession of class B drugs after a stop and search in the Pollards Hill area in south London. The incident is not been treated as terror-related, and investigations are being led by specialist homicide investigators. “We are doing all we can to establish a motive for the murder,” the police chief added. Body-worn cameras are being analysed to establish how the gun escaped detection. According to the IOPC, police were about to run a metal detector over the suspect before he managed to reach a gun he had concealed on his body and open fire, fatally shooting the sergeant in the chest and himself in the neck. The suspect is understood to have been referred to Channel, an arm of the government’s anti-extremism Prevent scheme. But he was not on the radar of the security services as a terror threat, nor is he understood to have been through the criminal justice system previously. Ratana was also a keen rugby player and coach, representing London Irish and the Met teams before turning to training others, most recently at East Grinstead, where he was the team’s head coach. The rugby club’s vice chairman, Matt Marriott, said two one-minute silences would be held on Sunday morning. “He wasn’t just a coach to the players. He was a role model, a mentor, and often actually a father figure. We’re going to mourn him as a family member. He’s left a big hole, to be honest.” 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 Fiona Bone, 32, and Nicola Hughes, 23, were killed in September 2012. Ratana leaves a partner and an adult son from a previous relationship. Dick said: “The safety of my officers is a top priority and very close to my heart. We are a large, professional, resilient, and very experienced police service. “As we mourn the loss of a much-loved colleague, senselessly killed, be under no illusion that our resolve to protect the public and to tackle violent crime – whoever may be responsible for it – will be undiminished.”