I'm the Girl He Wants to Kill(1974)

Overview:

Returning home to her flat, Ann Rogers passes a stranger leaving the building. A few moments later she discovers her neighbor lying dead in the hallway, the latest victim of a serial killer. Ann could be able to identify the killer, but the killer also knows her face and knows he needs to silence the witness... TV episode from the series, "Thriller" was also released as feature film on home video starting in the 1980s.