A police officer who shot dead an innocent man he suspected of being a terrorist following the 7/7 London bombings has spoken for the first time about the killing.

Jean Charles de Menezes, a 27-year-old electrician, was killed two weeks after suicide bombers targeted three London Underground lines and a bus on July 7, 2005, killing 52 people.

Now one of the firearms officers who shot Mr de Menezes has defended his actions, saying he was certain “we will die” if he did not act.

Mr de Menezes, who was from Brazil, lived in a block of flats that had been linked to one of several suspects who had planned to target the capital’s transport network for a second time on July 21.

The next day, Mr de Menezes was followed by officers and shot seven times by two gunmen in a train carriage at Stockwell tube station in south London.

“Reliving this in detail is painful,” the officer, known only as C12, said in the Channel 4 documentary Shoot To Kill: Terror On The Tube.

“I want to make sure people understand these decisions, while they are made quickly, they are not made lightly.

“Because of his actions, what he did, the information we got, it left me with no other conclusion than I had to act or we were going to die.”

The printer claimed that Mr de Menezes’ behavior led him to believe the electrician was about to detonate a bomb.

The way Mr De Menezes stood up “triggered” something in his head, C12 claimed.

“He knew who we were. He still continued his forward momentum while I had my gun raised, pointing at his head,” the officer recalled.

Read more: Jean Charles de Menezes’ family say ‘we will never get justice’

“I remember the supervising officer then being in full contact with him and apparently what he was trying to do was get his hands so he couldn’t detonate.

“I expect an explosion at any moment, he will explode. We will die. But this is the essential.

“If I don’t do something now, we’re all going to die.”

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Two days after he was killed, Scotland Yard confirmed that Mr de Menezes was not connected to the July 21 attacks.

Dame Cressida Dick, who was promoted to Metropolitan Police Commissioner in 2017, led the operation in which Mr de Menezes died.

A jury cleared her of any fault in his death, but the Met was fined £175,000 with costs of £385,000 after being found guilty of endangering the public.

Shoot To Kill: Terror On The Tube will be shown on November 10 and 11 on Channel 4.