A police sergeant shot dead in Croydon was a New Zealander who had been working for London's Metropolitan Police for decades.
The officer, who has been named as Matiu Ratana originally from Hawke's Bay, was shot at the Croydon Custody Centre, a police facility in the south of the British capital, in the early hours of Friday morning (GMT).
A minute's silence has been held for the officer described by the Met Police chief as a "much-loved colleague".
The sergeant was shot in the chest when a man, who was being detained, produced a gun during a search.
The police said the suspect, aged 23, then turned the gun on himself and was now in a critical condition after being treated for gunshot wounds.
He was also under arrest on suspicion of murder.
BBC Home Affairs correspondent Danny Shaw said it was believed the suspect was known to counter-terrorism police having been on their radar in the past, though the Met Police has not officially confirmed that.
The policeman, understood to have been a few weeks away from retirement, was treated at the scene but later died in hospital.
The London Metropolitan Police commissioner Cressida Dick said: "We are all deeply shocked and very sad.
"I have visited and spoken to our officer's partner together with other colleagues, and we are of course giving her the best support we can. My heartfelt condolences go to her, to their family, to his colleagues and his close friends.
"A murder investigation is under way and officers are working at several crime scenes to secure evidence and to establish the facts of what happened."
The British Prime Minister Boris Johnson has paid tribute, saying: "We owe a huge debt to those who risk their own lives to keep us safe."
In a post on social media he added: "My deepest condolences go to the family, friends and colleagues of the police officer who was killed in Croydon."
Det Insp Richard Berns described his colleague as "hard working and an inspiration to all who knew him".
"It was a privilege to have worked with him and known him over so many years," he said.
"He was was one of a kind and will be deeply missed. Rest in peace my friend."
Community police officer Jacqueline Kufuor was among those laying flowers outside the custody centre in tribute to her colleague.
She described the officer as "a lovely guy" and "the nicest man I have ever met".
The police said none of their weapons were fired during the incident.
An investigation by the Independent Office for Police Conduct (IOPC) is under way and will have several strands, our correspondent Danny Shaw added.
"It's likely to focus on the circumstances of the man's arrest - which officers were deployed during the operation; whether and how the suspect was searched; and if he was put into handcuffs," he said.
"The IOPC will also need to establish what happened at the police station and whether appropriate measures were put in place when the suspect was taken out of the police van."
The Mayor of London Sadiq Khan said the police were currently "reviewing the safety of custody suites" and "there could be changes very soon to custody suites to make sure they are as safe as they can be".
'Sick to their stomachs'
Ken Marsh, chairman of the Met Police Federation, said news of the shooting was "utterly devastating".
"Officers across London are in shock and sick to their stomachs at the nature of his death," he said.
"Sadly, on very rare occasions officers make the ultimate sacrifice whilst fulfilling their role.
"When that happens we will ensure their bravery and sacrifice is never forgotten."