On dead rising how do you kill the prisnors on the hummer jeep lookin thing?

i tried everything i ve gotOn dead rising how do you kill the prisnors on the hummer jeep lookin thing?I walked around the edges outside till I found a underground parking garage. There are Tons and Tons of Zombies in there so just run through them. Eventually you will find some cars or a truck you can get into. Get into it and then drive it back out. Then you can hit them with the car and it usually kills one or 2 of them. Then you can get out and finish the last guy or just try to keep ramming them. That is how I did it.