NEW YORK — A man charged with killing eight people by driving a truck down a lower Manhattan bike path in October 2017 recently threatened to decapitate an officer at the jail that has housed him since his arrest, U.S. prosecutors said.

In a Tuesday night court filing, the Department of Justice said Sayfullo Saipov made the threat on Dec. 18, after the officer’s supervisor told him to stop obstructing a security camera in his cell at the Metropolitan Correctional Center in Manhattan.

Prosecutors said they want to introduce the incident as “proof of future dangerousness” during the penalty phase of Saipov’s case, if he is convicted at his April 20 trial.

Saipov, a 32-year-old Uzbek national, has pleaded not guilty to charges including eight counts of murder, 18 counts of attempted murder and providing material support to Islamic State militants. He could get the death penalty if convicted.

Federal public defenders representing Saipov did not immediately respond on Wednesday to requests for comment.

Since terrorist Sudesh Amman was released early from his sentence last month, going on to stab two people in Streatham, London, Downing Street has been urged to confront the threat of extremism in jails.

It is believed that Imiuru’s attempt to copy jihadist methods will be a concern to those in the prison service.

Speaking to the Times, former prison governor Ian Acheson said the attack was ‘disturbing’.

Mr Acheson had conducted an official review of prison extremism in 2016 and said the attack suggested ‘careful pre-meditation at the least’.

‘The attack could well have been inspired by recent violent extremism inside and outside the prison walls.

‘It’s extremely important that the police investigation is speedy and transparent and that a terrorist motive is thoroughly investigated’.

London Bridge attacker Usman Khan used the method of strapping weapons to his arm, it was also used in the 2017 attack