MARSHALL COUNTY, Ind. (WOWO): Indiana Conservation Officers are investigating an accident involving a grenade launcher. 41-year-old Kevin Patterson, of Walkerton, was injured after he fired a starburst grenade round from an AR-15 platform rifle. It happened at a private shooting range on Plymouth-LaPorte Trail in Marshall County. Officers say the grenade went off in the launch tube under the rifle barrel. Patterson was taken to Methodist Hospital in Indianapolis for treatment of injuries to his arm. Police are still investigating.