Our police officers are under siege:

DALLAS — He served his country overseas. Then he came home, became radicalized, and turned into a mass murderer.

Micah Johnson, 25, of Mesquite, Texas, was identified by police as the sniper who shot 12 people during a Black Lives Matter protest in downtown Dallas on Thursday night. By Friday, the authorities had found “bomb making materials, ballistic vests, rifles, ammunition, and a personal journal of combat tactics” in the Army veteran’s apartment—evidence suggesting that the killings might have been only one part of Johnson’s violent plans.

Johnson left the Army “under a cloud of sexual harassment charges made by a fellow soldier who sought an order of protection against him and said he needed mental health counseling.” And on social media, Johnson left traces of a militant mindset. Johnson’s profile photo on Facebook shows him in a dashiki, holding a clenched fist in the air. Johnson’s cover photos are a black liberation flag and a black power fist.