A suspenseful moment is right at the beginning. The music helps build up the suspense. At first it is playful, but then it combines with the camera to reveal something is not right. The music combines with a Jump cut showing a dead body. This creates suspension effectively.
Another suspenseful moment created is when the Stepfather is in the middle of suffocating the father of the children and ex-husband of the mother. We are shown the struggle between the killer and the victim, during which the son of the victim is about to walk in the room and witness the attempted murder.
Lastly another suspenseful moment is when the son realises that the killer will make his mother the next victim. The fight between the son and the killer builds up sense as it looks as though either of them could be dead, and then they come back, whilst you are willing for the killer to be defeated.