A Metropolitan Police officer was shot dead at a police station today by a suspect who turned the gun on himself but is still alive.
The officer was shot at 2.15am this morning by a man being detained for an unknown reason at Croydon custody centre in South London.
Officers and London Ambulance Service paramedics treated the officer at the scene before he was taken to hospital where he later died.
It is believed to be the first time a police officer has been shot and killed on duty since September 2012 when Dale Cregan killed PCs Nicola Hughes and Fiona Bone.
The man was being detained at Croydon custody centre in South London (file picture)
Detectives said a 23-year-old man was arrested by officers at the scene and taken to hospital with a gunshot wound, where he remains in a critical condition.
Scotland Yard said no police firearms were discharged, and they were informing the officer's relatives and supporting them with specialist officers.
Commissioner Cressida Dick said: 'This is a truly shocking incident in which one of our colleagues has lost his life in the most tragic circumstances. My heart goes out to his family, direct colleagues and friends.
'We are currently supporting his family and also have a dedicated team providing support to the officers and those in the custody centre who witnessed the shooting.
'When a colleague dies in the line of duty the shockwaves and sadness reverberates throughout the Met and our communities. Policing is a family, within London and nationally, and we will all deeply mourn our colleague.
'We are in the early stages of the investigation and are still working to establish the circumstances surrounding the incident and we will provide further updates when we have them.'
Scotland Yard said it had referred the incident to the Independent Office for Police Conduct which will lead an independent investigation.