NEW YORK, United States (AFP) – US authorities Monday released video of a black Muslim man shot dead by police and the FBI in Boston, and accused of planning to behead police officers.

The grainy video was filmed by a surveillance camera fixed to a Burger King about 50 yards from the confrontation with Usaamah Rahim, a 26-year-old security guard, in a parking lot.

Police say Rahim was killed after he refused multiple demands to drop a military-style knife. Those demands are not audible, nor is the weapon clearly visible on the video.

The footage shows Rahim walking towards a bus stop, officers approaching him, then retreating and then Rahim falling to the ground.

District Attorney Daniel Conley said he was releasing the video to clamp down on “rumors and bad information” as he investigates whether Rahim’s killing was lawful. It was just one piece of evidence among many, he said.

Rahim’s family, who initially claimed he was shot in the back at a bus stop, was shown the footage last week before his funeral.

“This unravelled very quickly. I think they made the right call,” Boston Police Commissioner William Evans told reporters Monday.

Court papers filed last week accused Rahim of buying three military-style knives from Amazon and deciding to “go after” the “boys in blue” because they were “the easiest target.”

An alleged associate, David Wright, 25, has been charged with conspiring to obstruct a federal investigation.

Court papers said Rahim had been “planning to engage in a violent attack in the United States” since May 26 — little over a week before his death.

On June 2, he allegedly telephoned Wright at 5:00 am to indicate that he planned to attack police officers. He was shot dead two hours later.