Head through the parking garage and open the door to the elevator controls room using the diamond key.
Resident evil 2 locked door parking garage.
From the parking garage head straight down the hall and go through the first door on your left to find the firing range.
Return to the parking garage and inspect the car key and look on the other side for an unlock button you can press which will pop the trunk of a nearby patrol car to the left of the door you.
Collect the blue herb high grade gunpowder white and the shoulder stock gm 79.
Be sure to check the elevator itself for a small note then head back.
Next to the magazine is the police station map b1 along the wall but the elevator controls room is locked by a diamond door.