Im trying to find this one serial killer movie from the 80s. I think it was called Mask but Im not sure. All I know is that the cover had a leather S&M mask with a zipper on the mouth. The movie was about this serial killer who would kill entire families. One of these families was having a party when they were all killed. I think this was an HBO movie but I'm not sure.
Sounds like "Blackout" - guy lowered the temp in a room to fool people with the actual time of death, I think....