Why is North Korea executing high-level officials with anti-aircraft guns?

North Korea has reportedly executed a top official, Defense Minister Hyon Yong Chol, in a most North Korean manner: by shooting him to pieces with an anti-aircraft gun in front of a crowd of hundreds of other officials.

That's according to South Korea's intelligence service, which has a history of exaggerating reports about North Korea that make the country look bad. But there's reason to believe this could hav