A POLICE officer has been shot dead in a London police station by a man who then turned the gun on himself.

The victim, said to be a "long-serving sergeant", died in hospital after the gunman, who was being detained, opened fire at Croydon custody centre in south London during the early hours of this morning.

The 23-year-old murder suspect is in a critical condition in hospital with a self-inflicted gunshot wound after he was held at the scene.

Scotland Yard said no police firearms were fired during the incident at around 2.15am.

Met 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."

Home Secretary Priti Patel added: "I am deeply shocked and saddened to learn that a Metropolitan Police Officer has been shot and killed in the line of duty.

"My thoughts today are with his family, friends and policing colleagues in London and across the country.

"This morning I spoke to Metropolitan Police Commissioner Cressida Dick to express my condolences and to offer whatever support is needed as this tragic event is investigated.

"This is a sad day for our country and another terrible reminder of how our police officers put themselves in danger each and every day to keep the rest of us safe."

The incident has been referred to Independent Office for Police Conduct watchdog which will lead an independent investigation. The Met continues to investigate the officer's murder.

Speaking at the coronavirus briefing in Edinburgh, Nicola Sturgeon said: "I wanted to take the opportunity to convey my deepest condolences to all of the officer's loved ones.

"This is a heartbreaking reminder of the danger police officers confront every single day on our behalf and of the enormous debt of gratitude we owe them as a result of that."

And Police Scotland's Chief Constable Iain Livingstone also paid tribute to the officer.

The head of Scotland's police service said: "Can I also start this afternoon by expressing on behalf of everyone in policing our deepest sympathies and support for our colleague from the Metropolitan Police who was tragically shot on duty in the early hours of this morning.

"And also support to our colleagues in the Metropolitan Police and indeed to the people of London, the thoughts of the whole of the policing family are with those who have lost a loved family member, a friend and a close colleague."

Scottish Justice Secretary Humza Yousaf also sent his condolences.

A statement posted on social media reads: “Dreadful news to wake up to this morning. My heart goes out to the family and friends of the officer killed & I know the wider police family will also be feeling this loss. A reminder our officer put themselves in harm's way every day to keep us safe, we owe them a debt we simply cannot repay.”

The officer's family is being informed.

Leroy Logan, a former Met superintendent, said there were questions to be answered around the circumstances which led to the shooting.

"How did that person come to be in the station, whether it's in the yard or the building itself, and be able to produce a weapon, whether it's on them at the time?" he told BBC News.

"It depends on the calibre of the weapon, because obviously if it's a small weapon and it can be easily in that person's clothing, then obviously it brings another question on how thoroughly that person was searched, if at all.

"Those are the things the department for professional standards will look at and the IOPC as well as the investigating officers who will have to look at this thing thoroughly."