Digger Harkness

Digger Harkness aka Captain Boomerang is a killer in Starling City.

Biography
As a man walked in an alley, Digger approached him and threw his boomerang, killing the man.

Trivia
The comic character he is based on is named George Harkness, as "Digger" was his nickname. George debuted December 1960 in Flash issue 117.