Green’s Dictionary of Slang

(US Und.) to threaten with a gun or weapon.

1973		J. Wambaugh Onion Field 96: [H]e’d grinned at Small just before he pulled down on him.
1981		H. Gould Fort Apache, The Bronx 48: You pull down on a dude with that nowhere piece, and then when he thinks he’s gonna get over on you, you blast him with El Tremendo.