Matt Ratana shooting: Police probe suspect's background in search for answers over custody killing

Police are probing the background of a man suspected of killing an officer in a south London custody suite before turning the gun on himself while in handcuffs.Sergeant Matiu Ratana, 54, died in hospital after the handcuffed 23-year-old opened fire at his chest in Croydon custody centre at around 2.15am on Friday.