A movie about a masked serial killer

Hey all.

I need help finding a movie I accidentally watched when I was little at the movie theater.

All I can remember is this: Two kids are camping in their backyard. They are in a tent, and they have a projector. They are watching photographs or a film. The mother is in the kitchen, preparing dinner or a snack. Suddenly, a masked person walks by the tent and inside the house, and kills the mother with a knife, I believe.

I’m sorry I can’t remember any more details, they only played that scene (by accident, I hope). In any case, it cost me a few sleepless nights. I hope you can help me find it, I’ve been wanting to watch it ever since.

Thank you in advance!