William J. Sharkey was a pickpocket, a con man, a politician, and a murderer, though whether or not that murder was an accident became the question at the center of a case that gripped New York for months. And then, he vanished. Sort of.
Research:

SYMHC Classics: COINTELPRO 1
39:12

Behind the Scenes Minis: It's Not Unprecedented
16:46

The Rendition of Anthony Burns, Part 2
43:32