Requires all DLC.
Much easier if you attempt this with a larger vehicle, the APC is probably the easiest just because of the fact that it is the largest. From there obviously you need people to attach to it. Your best bet is parking it near the curb in a crowded area, crouching, pointing your weapon at it, and firing whenever anyone walks between you and the vehicle.
If you have a co-op partner this can get a little bit easier as he can drive around the crowds slowly as you peg them to it.