An employee of a Hightstown apartment complex suffered a stomach injury Monday morning when the fuse of deactivated grenade exploded, borough police said. The incident occurred at about 11:40 a.m. at the Deerfield-Westerlea Arms apartments. Borough police responded to a call at that time for report of a 39-year-old woman with severe stomach pain, the police department said in a statement. Officers arrived to find the woman was injured by a grenade. They arranged for Robbinsville EMS to take her to a hospital, then shut down the area, evacuated some residents and called the fire department and …