Who was the killer?

the killer was the old guy that was supposedly "helping" her all along. the secret room was used to videotape people for future blackmail. hope that helps!

Her aunt was taping her mother and the doctor because she had become suspicious of the doctor. When she discovered the doctor's inappropriate behavior and stupidly told him, the doctor killed her and blamed it on her mother to cover for him. He then manipulated both mother's and daughter's memories under guise of therapy over the subsequent years.

The Terminator.

When there's no more room in hell, The dead will walk the earth...