(AP) - The father of slain Mount VernonOfficer Christopher Ridley is claiming his son was shot to death point-blank by a fellow officer who knew he was a cop.

The claim challenges a grand jury finding that Ridley was shot from across the street by Westchester County policemen after he displayed a gun and failed to identify himself as an officer. The county officers were cleared.

Ridley was gunned down in 2008 as he tried to arrest an assault suspect while off-duty in White Plains.

In his lawsuit, Stanley Ridley claims Westchester District Attorney Janet DiFiore is leading a cover-up of the circumstances, including that one of the officers fired at him from close range.

DiFiore dismissed the lawsuit, calling it outrageous.