I'm trying to find the name of a sci-fi/horror movie that would've been released in the US sometime in the late 1970s or early-to-mid 1980s. My parents recorded it from cable, so it would've been on either HBO or Showtime back in those years. I always thought the name was "Disturbing Behavior", but that's a film from 1998. I probably got them mixed up because of the similar premise.
The one I'm looking for has a mad scientist type taking control of people in a small town using some form of hypnosis/brainwashing. Unlike "Disturbing Behavior", I don't think any kind of technology was being put into their heads. The main scene I recall was that the scientist demonstrated his power to the protagonist (town sheriff, maybe?) by forcing his teenage son to slit his wrists in front of him. In case it makes a difference, the son sliced his forearms lengthwise instead of horizontally across the wrists. I want to say the movie ended with the antagonist winning and the protagonist joining the modified townsfolk.