It's not wise to threaten a hitman.
A gangbanger tries to cash a check, not realizing the man behind the counter has a side gig where he gets paid to kill people. Sometimes, threats can lead to freebies.
This story first appeared in Fantastic Stories of the Imagination. Strange place to find a crime story, but there you go. The story also appears in Quick Shots and The Hitman Stories (an omnibus edition of all 6 hitman stories).