Without discounting the Saudi connection, my first thought when I heard was that it sounded kinda biker style. This seems more like a criminal hit than an international terrorist attack.
The reason I shy away from that theory is that this guy was just a (very) high level bureaucrat. Decisions about prisoners are generally made by others. One thing he was directly involved in, however, were some painful decision about prison closings, which can have a big effect on a small town's economy.