A police officer shot dead in South London has been named as Sergeant Matiu Ratana.The 54-year-old died in hospital after a handcuffed suspect opened fire at Croydon Custody Centre in the early hours of Friday.The 23-year-old suspect, who had been arrested for possession of Class B drugs with intent to supply and possession of ammunition, also shot himself during the incident at about 2.15am and is in a critical but stable condition in hospital.No police firearms were fired and the case is not