North Korea executed its defense chief by putting him in front of an anti-aircraft gun at a firing range, Seoul's National Intelligence Service told lawmakers, which would be the latest in a series of high-level purges since Kim Jong Un took charge.Hyon Yong Chol, who headed the isolated nuclear-capable country's military, was charged with treason, including disobeying Kim and falling asleep during an event at which North Korea's young leader was present, according to South Korean lawmakers briefed in a closed-door meeting with the spy agency on Wednesday.His execution was watched by hundreds of people, according to NIS intelligence shared with lawmakers.[...]The lawmakers said Hyon, 66, was executed at a firing range at the Kanggon Military Training Area, 14 miles north of Pyongyang, according to the NIS.The U.S.-based Committee for Human Rights in North Korea said last month that, according to satellite images, the range was likely used for an execution by ZPU-4 anti-aircraft guns in October. The target was just 100 feet away from the weapons, which have a range of 8,000 meters, it said.