The flag outside Hertfordshire Constabulary's headquarters is at half-mast in memory of the police officer shot in London.

A custody sergeant died in hospital this morning shortly after he was shot by a man police had detained at Croydon Custody Centre.

Tributes have poured in for the officer, including from Hertfordshire's Chief Constable Charlie Hall.

He said: "I would like to extend heartfelt condolences from our policing family here in Hertfordshire to colleagues at the Metropolitan Police Service following this morning’s tragic news.

"Our thoughts are with the officer’s immediate family and friends, as well with colleagues from the whole force and community."

Watford Observer:

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Met Commissioner Cressida Dick has confirmed a murder investigation is underway, with a 23-year-old man arrested in connection with the shooting.

Ms Dick said: "The Met is a family. Policing is a family in London and across the United Kingdom.

"Today, we police are all mourning a great loss. I would like to thank our officers and the staff, together with colleagues from the London Ambulance Service, the London air ambulance and all our medical and hospital colleagues who I know did everything they could to save his life.

"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. We are working closely with the Independent Office for Police Conduct.

"Early indications are that the suspect shot himself. This has not yet, of course, been established as a fact. The man, I can tell you, remains in a critical condition in hospital.

"This terrible incident underlines again how police officers face danger every single day, 24/7, 365, in their work to protect our public."

Watford Observer:

Croydon Custody Centre. Credit: PA

Prime Minister Boris Johnson tweeted: "My deepest condolences go to the family, friends and colleagues of the police officer who was killed in Croydon last night. We owe a huge debt to those who risk their own lives to keep us safe."

London mayor Sadiq Khan tweeted: "Devastated by this news. My heart goes out to the family of this brave officer, who has paid the ultimate price for helping to keep Londoners safe.

"Tragic incidents like this are terrible reminders of the dangers our police officers face every single day."

Watford Observer:

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The Met said in a statement this morning: "At approximately 0215 on Friday, September 25 the officer was shot by a man who was being detained at Croydon Custody Centre in Windmill Lane.

"Officers and paramedics treated him at the scene and he was taken to hospital by London Ambulance Service. Very tragically he subsequently died at hospital.

"We are in the process of informing all of the officer’s family and are supporting them with specialist officers.

"A 23-year-old man was detained by officers at the scene. He was also taken to hospital with a gunshot wound and remains in a critical condition.

"No police firearms were discharged during the incident."