Here's an interesting story about an SUV and a train, together used as a murder weapon. Since trains and cars are already registered in California, I expect they'll just ban them outright. It's kinda like the old saying "prevent forest fires, register matches". It is also quite possible that handguns will be banned in California as a result of this because, with the killer's past history of suicidal behavior, he must certainly at least have considered using a handgun at some time.
http://www.foxnews.com/story/0,2933,145548,00.html