In the DC comics, the Longbow Hunters are a villainous group led by Ricardo Diaz, created to take down Green Arrow. Members of the group include Count Vertigo, Brick, and, as on the show, Red Dart.
At the beginning of the episode Rene said "This psycho has been MIA for five months (talking about Díaz), and then he goes after Oliver and Felicity." This is actually a mistake since Oliver is still in prison. He should have said "Felicity and William" instead.