Although it is most certainly not the actor's (Tony Beckley's) fault because he was terminally ill during production, the killer Curt Duncan looks far too physically frail to have realistically torn two children apart with his bare hands.
In the final scene, Jill goes to her bedroom closet to see if Curt Duncan is in there. She is about to open the door with her left hand. In the next shot, she opens it with her right hand.
When Jill has a drink at the wet bar, the grandfather clock is visible in the shot, about a foot to the right of the bar. In all other shots the clock is about four to five feet from the bar, much closer to the hallway.
Based on the year the film took place, 1 minute would not be nearly long enough to trace Curt's call. Back when the movie was set, it would've taken 10-20 minutes for several switchboards and circuits to locate the origin of the call.