when u get a car go down into the tunnels then turn rite then take ur 1st left then take another rite and u shud end up in a parking space with a door there go through the door and the key is at the back

I suggest you get the car rather than taking the motorcycle before heading to the tunnelz.Once uz inside the car head to the tunnelz,after the loading part when you just left from the parking lot now inside the tunnels..you will choose from a right or left turn...choose the right turn,drive straight ahead and make an upcoming left turn and drive up ahead to another right turn that leads to a dead end with the door leading to the warehouse having boxes,one sub-machine gun and the tunnel key ya folkz looking for.

kill all the zombies in the tunnel by the meat area place thing and in it to and there it is by the trucks

when you're in the room with the 2 sledge hammers go all the way down into the room and make a right behind some boxes. There you'll find the key.