Looking for a horror movie from the 1980's played on HBO, a group of teenagers go camping, the killer is a man that killed or his mother died( can't remember) and he keeps her in the cabin, he hunts them killing most , he would dress up as his mother (sometimes). Can anyone help please... Thanks!

The only one I can think of like that is Back Woods, but that wasn't made until 2001

Back Woods (Video 2001) - IMDb

The Final Terror (1983)

You can read the plot summary here, including the twists:
The Final Terror - Wikipedia, the free encyclopedia

What a great cast!
John Friedrich: Dennis Zorich
Rachel Ward: Margaret
Daryl Hannah: Windy Morgan
Adrian Zmed: Marco Cerone
Lewis Smith: Boone
Joe Pantoliano: Eggar
Akosua Busia: Vanessa
Mark Metcalf: Mike
Jim Youngs: Jim