of a suspenseful moment.
In the beginning when we realise that the stepfather has killed the family, the stepfather stands in front of the door with he camera positioned at the back of him in a medium close up shot. Then suddenly the camera starts to shake and zoom in at the back of him while a high pitch music is being played at the background, it made me feel all uncomfortable.
Another aspects is Alfred's Hitchcock's "Bomb Theory" = audience knows something that the character doesn't. Example: Stepfather who is a family killer talk to woman in the shop.