To shoot someone in the head.
From "The Godfather", when Michael tells Sonny he wants to kill the Police Captain.
Sonny: Hey, whataya gonna do, nice college boy, eh? Didn't want to get mixed up in the Family business, huh? Now you wanna gun down a police captain. Why? Because he slapped ya in the face a little bit? Hah? What do you think this is the Army, where you shoot 'em a mile away? You've gotta get up close like this and bada-bing! You blow their brains all over your nice Ivy League suit.