While playing with Carlos in Resident Evil 3: Remake you have to open the shower wall using explosives that another policeman was about to use but did not have the batteries. However, after reading a note in the shower, you find out that there is some left in the safe on the first floor.
You have to catch the explosives from the second floor shower room. You need it to access the STARS offices located on the other side, in the hallway. Grab the explosives from the wall, then you need to grab the batteries locked in the security deposit room, which is locked.
You can find the key above some boxes on the third floor. Get out of the shower and continue as you come, except go left, go up the stairs to retrieve the key to the safe. Go back down and go up to the first floor. You will fight a zombie in the stairwell, then a licker will block your path. When you enter the room, you must use the electronic terminal and type in which locker you want to open. The batteries are in locker 104.
You can also type in codes for 106 to gain access to 30 assault rifle rounds and 109 to get a grenade in the security deposit room.
