A former Black Lives Matter activist is making stunning accusations against fellow agitators in an unprompted YouTube video.Trey Turner, who says he protested police killings in St. Paul, Minnesota, created a video to expose what he learned while he was active with the group.Turner said he joined Black Lives Matter after the shooting of Jamar Clark last March, and that he was a part of the “4th Precinct shutdown.” He said he joined because activists insisted the movement was peaceful and “didn’t hate whites.” According to Turner, he was an active participant in the protests at the governor’s mansion after...