A long-serving cop has been shot dead at Croydon Custody Center in south London.
The male sergeant was shot in the chest before the speculate turned the gun on himself, sources have told the BBC.
The man had been brought to the guardianship suite in a police vehicle and the shooting occurred during addressing about Covid-19, the BBC was told.
Brief's quiet has been held for the official portrayed by the Met Police boss as a "much-adored partner".
The person in question, who has not been named, is thought to have been half a month from retirement and was portrayed as "exceptional" by a partner.
BBC Home Affairs journalist Danny Shaw said it was accepted the suspect - who is fundamentally sick in clinic - was known to counter-psychological oppression police having been on their radar before, however the Met Police has not authoritatively affirmed that.
The man, who is thought to have been kept for having ammo, has since been captured on doubt of homicide.
No police guns were released during the occurrence, which occurred at about 02:15 BST at the Windmill Road focus.
The Met boss said the policing family was "profoundly stunned and miserable" after the demise of the official.
"I have visited and addressed our official's accomplice along with different partners and we are obviously giving her the best help we can," she said
"My ardent sympathies go to her, to their family, to his partners and his dear companions.
"A homicide examination is in progress and officials are working at a few wrongdoing scenes to make sure about proof and to build up the realities of what occurred.
"Early signs are that the presume shot himself, this has not yet obviously been set up as a reality."
Det Insp Richard Berns portrayed his partner as "dedicated and a motivation to all who knew him".
"It was a benefit to have worked with him and known him over endless years," he said.
"He was exceptional and will be profoundly missed. Find happiness in the hereafter my companion."
Network cop Jacqueline Kufuor was among those laying blossoms outside the authority place in accolade for her associate.
She depicted the official as "a flawless person" and "the most pleasant man I have ever met".
An examination by the Independent Office for Police Conduct (IOPC) is in progress and will have a few strands, our reporter Danny Shaw included.
"It's probably going to zero in on the conditions of the man's capture - which officials were conveyed during the activity; regardless of whether and how the suspect was looked; and in the event that he was placed into binds," he said.
"The IOPC will likewise need to build up what occurred at the police headquarters and whether proper measures were set up when the suspect was removed from the police van."
Prior, Prime Minister Boris Johnson stated: "We owe a tremendous obligation to the individuals who hazard their own lives to guard us."
In a post via web-based media he likewise stated: "My most profound sympathies go to the family, companions and partners of the cop who was executed in Croydon the previous evening."
By Dominic Casciani, BBC Home Affairs journalist
This horrifying occurrence in Croydon gives off an impression of being completely one of a kind - an official shot by a man who was at that point inside a police office - and the stun felt today underlines how uncommon it is for cops in the UK to be killed by a suspect in the line of obligation, comparative with different countries.
The Metropolitan Police official shot dead in Croydon is the seventeenth from the power to have been killed by a gun since the Second World War.
In any case, since the start of the twentieth Century 73 cops have been shot and murdered by lawbreakers in the UK, barring all passings in Northern Ireland.
Most of those passings - more than 50 - have happened since 1945.
Cops in different pieces of the world are frequently bewildered why British constables are not regularly equipped. However, the truth of the matter is that there are not many criminal firearms available for use - and the way of life of policing has never considered it to be worthy to be all around outfitted.
Be that as it may, Tasers are progressively a typical sight in the UK - and a monstrous review of cops as of late discovered 75% would convey one of the not exactly deadly gadgets on the forefront, whenever given the decision.
Yogarajah Emmanuel, 43, who runs a shop inverse the authority suite, said he woke up at 02:30 BST to the sound of alarms.
"I watched out of my window and could see three ambulances," said Mr Emmanuel.
"There was commotion and out of nowhere one emergency vehicle from inside the vehicle leave came out and hurried off.
"Today I heard it was a cop and just felt so pitiful. They are on the whole generally excellent individuals and wave and make proper acquaintance when they go to my shop."
Met Police officials have been remaining external the authority suite accomplishing something they fear - grieving one of their own.
A few bundles of roses have been put outside the structure in memory of the sergeant who was shot.
Occupants who live inverse have shared their stun and mistrust that such an unfortunate homicide has happened so near and dear.
Measurable groups have been seen in the close by yard gathering proof, while different officials can be seen inside the suite continuing with their obligations.
'Debilitated to their stomachs'
Ken Marsh, executive of the Met Police Federation, said updates on the shooting was "totally destroying".
"Officials across London are in stun and wiped out to their stomachs at the idea of his demise," he said.
"Unfortunately, on uncommon events officials make a definitive penance while satisfying their job. At the point when that happens we will guarantee their grit and penance is rarely overlooked."