Kill? No...
Flatten every joint in his fingers and toes with a ball peen hammer? Much better. Takes a while to do it properly, too. Remember to sterilize each blow with iodine. Drop him off at the local hospital afterwards, of course, but don't slow down much when tossing him out of the van. The hospital bills plus the crippling effects should slow him down on the rape spree.
Or pick up a bunch of crack, packaged individually, smash in the window of his car, drop it in the glove box / seat and call the law to report a stolen car. Probably get him a decent length of time in the lockbox, and by the sounds of things, a serious investigation in his life might turn up some more facts that are interesting to a Judge.
Get the girl signed up on one of those 2 way voice monitor house alarms. And get her a carry permit, some training, and a firearm.