Updated

The district attorney in Las Vegas says mistakes were made, but no criminal charges will be filed against a police officer who shot and killed an unarmed, disabled Gulf War veteran in his car in December 2011.

Clark County DA Steve Wolfson issued a report Thursday saying that Officer Jesus Arevalo thought he was shooting in self-defense when he opened fire with an assault-style rifle, killing Stanley LaVon Gibson.

In fact, what Arevalo heard was another officer firing a beanbag shotgun to break a side window of Gibson's vehicle.

A grand jury previously refused to indict in the case.

Attorney Cal Potter represents Gibson's widow, Rondha Gibson, in a federal lawsuit accusing Las Vegas police of civil rights violations.

Potter says he didn't expect that the county DA would prosecute.