止まらないと撃つぞ。

to stop (moving); to come to a stop; to stop (doing, working, being supplied); to come to a halt; to cease; to be stopped; to be suspended; to alight; to perch on

if; when; and; with; particle used for quoting (with speech, thoughts, etc.); quoting particle; promoted pawn; indicates question (sentence end)

to shoot (at); to attack; to defeat; to destroy; to avenge

(sentence end) adds force; indicates command