The young son of a Washington state cop picked up a gun he found in his absent dad's van and fatally shot his 7-year-old sister. The girl and her younger brother were waiting in the van while their parents were nearby outside, said a Marysville police officer. "At this time we are all extremely concerned for the well being of one of our department family members," said Police Chief Rick Smith. Police have not revealed how long the children were alone in the car, and where the gun was kept, reports the Seattle Times. An investigation is continuing.