A witness in the shooting death of off-duty Mount Vernon Officer Christopher Ridley went public Wednesday.

Efrem Burgos, 51, claims he saw Westchester County Police Officer Frank Oliveri shoot Ridley in the head point-blank during a friendly fire incident in 2007.

"Officer Ridley was falling back with his hands open, but still holding his gun for dear life," says Burgos. "As he was falling down ? Officer Oliveri came from behind the tree - he was using it for cover at that time - and [shot Ridley] right in his head."

Oliveri and three other officers were later cleared of any wrongdoing by a grand jury, but Ridley's father disputes the decision and has brought a $90 million wrongful death lawsuit against the county.

Burgos is also suing Westchester County, claiming officers harassed and arrested him numerous times after the incident to keep him quiet.