While playing as Carlos in Resident Evil 3: Remake you need to blow open the shower wall using some explosives another cop was about to use but didn’t have the batteries for. However, after reading a note in the shower, you discover there are some left in the Safety Deposit room on the first floor.
You need to grab the explosives from the shower room on the second floor. You need it to gain access to the S.T.A.R.S offices located on the other side, down the hall. Grab the explosives from the wall, and then you need to grab the batteries locked in the Safety Deposit room, which is locked.
You can find the key on top of some boxes on the third floor. Go out of the shower and proceed the way you came, except go to the left, up the stairs to grab the safety deposit key. Proceed back down, and to the first floor. You will fight one zombie on the stairwell, and then a licker will block your path. When you enter the room, you need to 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 obtain a grenade while in the Safety Deposit room.