36 Grenade Rounds
On the path leading to the Sales Office in the Uptown you will find a Square Crank lying on the floor. Now head back to the back alley where you saw Brad shooting at a few zombies before running off earlier on in the game. Next to the discarded toy boxes is a shutter that's been pulled down. Use the Square Crank in the device next to the shutter to open it, revealing three lots of 12 Grenade Rounds.
There's only point in doing this if you grabbed the Grenade Launcher from the Sub Station. If you forgot it, or haven't been there yet, then be sure to grab it!
Added by: Volke Apr 11th 2009, ID#15519