A long-serving police officer has been shot dead at Croydon Custody Centre in south London.
The male sergeant was shot in the chest before the suspect turned the firearm on himself, sources have told the BBC.
The man had been brought to the custody suite in a police vehicle and the shooting happened during questioning about Covid-19, the BBC was told.
A minute's silence has been held for the officer described by the Met Police chief as a "much-loved colleague".
The victim, who has not been named, is thought to have been a few weeks away from retirement and was described as "one of a kind" by a colleague.
BBC Home Affairs correspondent Danny Shaw said it was believed the suspect - who is critically ill in hospital - was known to counter-terrorism police having been on their radar in the past, though the Met Police has not officially confirmed that.
No police firearms were discharged during the incident, which happened at about 02:15 BST at the Windmill Road centre.

Police officer shot dead at Croydon Custody Centre
The long-serving sergeant was an "inspiration to all who knew him", says one colleague.
www.bbc.co.uk
How terribly sad.
You have to wonder though that why wasn't the suspect in handcuffs?
RIP.