Green’s Dictionary of Slang

1. (US black) to kill; thus sniping n., killing.

1935		B. Traven Treasure of the Sierra Madre 103: ‘As soon as he comes, snipe him and be done with it.’ [...] ‘There’s no sense in shooting the man down at sight [...] It’d be a crime to snipe a harmless hobo.’.
1971		J. Bouton I’m Glad You Didn’t Take it Personally 136: ‘If the Commissioner cuts off greenies because of your goddam book, I personally will snipe your ass’.
1980		E. Folb Runnin’ Down Some Lines 107: The act of killing (wasting, icing, offing, chilling, sniping, snuffing).

2. (US black) to promote by affixing an advertisement to an one already posted by another.

2005

B. Coleman Rakim Told Me 127: Keith and I handled the street promotions on all of our albums. We sniped everywhere. We'd be out early in the morning putting up posters all over the tri-state [area].