Leave abruptly or hurriedly, as in I'm just going to pop off and mail some letters.
Die suddenly, as in No one expected her to pop off like that. [Colloquial; second half of 1700s]
Speak thoughtlessly in an angry outburst, as in Don't pop off at me—complain to whoever's responsible. [Slang; c. 1930]
pop someone off. Kill someone, as in The sniper popped off at least three men. [Slang; early 1800s] All four usages transfer pop in the sense of “explode” to other kinds of sudden or violent behavior.