Bob

Bob is an undercover thug whom Robert Thorne hired to join his gang of menions. After he killed Two-Face, on Thorne's demand, Bob revealed himself to be Robin. Then Bob, along with his partner John Smith (who is actually Batman), pull out their guns and kill Thorne

Trivia

 * It's distintivly easy to figure out that Bob is Robin, because 1) they both wear green masks and 2) they have the same hairstye.