The family of an Ohio Wal-Mart customer fatally shot by police as he held a store BB gun filed a federal lawsuit Tuesday claiming officers and the retailer are negligent in his death. The suit says the Beavercreek Wal-Mart was at fault for allowing the Crosman MK-177, which resembles an AR-15 rifle, to be left unlocked on a shelf for two days. As a result, 22-year-old John Crawford III was able to pick up the gun on Aug. 5 and walk around the store freely — an act that led to the tragic killing of the father of two young children, his family’s lawyers say.