name of an 80's horror movie ?

hey guys!!

i want to know if anyone of you can help me with this!

i remember i saw a movie looong time ago, it was an 80's horror movie, i cant remember quite well what was the plot, but i do remember the ending,, i know its kinda hard to help me but, here i go!

at the very ending, there's two dead men on the floor, they killed each other cause they were helping a girl to find out who was the killer (each guy thought the other guy was the killer). the girl was there thinking it was all over, but all of a sudden, the phone starts to ring,

and this girl turns around and sees a guy with a mask (a creepy old man mask), walking down the stairs, he was the killer!

and she just sat down waiting for her death!

please guys i know this is only for hardcore horror movie fans!