NEW YORK (AP) — Federal prosecutors have decided not to bring criminal charges against a white police officer who fatally shot a mentally ill black man who had accidentally set off his emergency medical alert device.

Acting U.S. Attorney Joon Kim said in a statement Thursday that he’d found insufficient evidence for charges against any of the officers involved in the 2011 shooting of Kenneth Chamberlain in White Plains, just north of New York City.

Chamberlain, 68, was home alone when he inadvertently triggered a medical alert on a console in his apartment. He told officers who responded to the call that he was fine and refused to open his door. He also tried to get the dispatcher at the medical alert company, Life Aid, to call off the police.

“I have the White Plains Police Department banging on my door, and I did not call them and I am not sick,” he said.

But the responding officers refused to leave. During a standoff that lasted more than 90 minutes, officers taunted Chamberlain with racial slurs. Chamberlain, a former Marine and correction officer, armed himself with a knife.

Finally, officers kicked in the door, zapped Chamberlain with a stun gun, shot him with beanbag ammunition and then killed him with a pistol shot.

Chamberlain’s family said the shooting was racially motivated.

The U.S. attorney in Manhattan opened an investigation after a state grand jury declined to indict the officers. Kim said the evidence indicated the officers believed that Chamberlain was threatening them with the knife.

A civil lawsuit filed by Chamberlain’s family was rejected by a jury in 2016.