RIP
TCM is one of the greatest examples of making a gruesome horror movie with limited on-screen gore. When I was a TA for film class, I used to teach the door slam scene during the lecture on Sound. The distant pig squealing, the crack that the hammer makes on Kirk's head, the guy's feet tapping at the floorboard as he twitches, and then Leatherface's final door slam as it's left to your imagination what exactly he's planning on doing with his body. It was a completely disgusting film with a reputation of being hard to distribute due to it's violent content, but most of it's appalling nature came from how the viewer had to jump to conclusions on what the Sawyer family did with their victims based on the shots and sound presented to obscure their violence.
Hooper had a ton of other great films like Poltergeist, but TCM, like the late George Romero's Night of the Living Dead, were able to do so much with a small budget and the basic special effects available in the 60's-70's.