That is so downright mean to come back again to vandalize your
vehicles. I still think a security camera might be able to catch these people
in the act. Then you would have pictures for the police to know who to
being looking for. They are surprisingly cheap considering. I googled up
a few.
http://www.google.com/products?hl=en...&um=1&ie=UTF-8

Who knows, maybe if they saw a camera watching, they would not be
so quick to come on your property again. I hope they are caught.