A Prince William County police officer was killed Monday afternoon in a wreck while responding to a call. Around 2 p.m., Officer Chris Yung, 35, crossed over the intersection at Nokesville Road and Piper Lane in Manassas while responding to a crash, according to a news release. A mini-van taking a left into the shopping center at the intersection collided with Yung, who was assigned to the county’s traffic unit as a motorcycle officer, police said.