The Last Diary of Nikita Rose (1970)

Nikita Rose's sister is attacked as they speak via a FaceTime call and never seen again. Exactly a year later, Nikita and her new partner Ben begin to notice odd things happening at night in and around their house. For her own peace of mind Nikita makes a Video Diary, filming everything including inadvertently the attacker, but after the odd incidents continue they decide to have Infra-Red CCTV installed. At this time Ben has to leave on business so Nikita invites her two friends over for company and drinks. That night her stalker attacks them all and all of the slaughter is captured by CCTV and Nikita's video camera.