The Backfire card says "The player who shot is the target of a BANG!" Does that mean that the player who shot is automatically a target of a Bang, or does the player playing Backfire need to use a Bang with it to actually backfire on the other player?
From the wiki page for bang
BackFire – Counts as Missed!. Any player who targeted you with Bang! is now a target of Bang!.
The card says it correctly that the payer who shot you is the target of a bang. If you needed to play a bang also for it to work that would be listed on the card as well.