He is well known for "Helter Skelter." He told his followers that this Beatles song was another prophecy of theirs that white people and black people would go to war, and essentially the black people would win. So his so solution was to just kill people.
In addition to using sex and drugs to control others and talk them into killing people, it was always suspected that he killed a few himself including a ranch hand where the "family" was camping. He is absolutely, awesomely insane but his death penalty sentence should have been carried out.