Wikia

The extra costumes in Resident Evil 2 can be obtained after getting the Special Key that will open the locker located in the Raccoon City Police Department's Dark Room . In order to get this key, the player doesn't have to pick up any kind of item nor killing a zombie until reaching the facility's entrance while playing in Normal or Hard mode. If done right, a zombified Brad will be down stairs in the small tunnel. It should be noticed that he's hard to kill and will inflict more damage to the player, and after defeating him, a player can obtain the special key.