Episode help?

Saw this episode a few years ago and would want to watch it again only i have no idea which one it is. What i remember from it is that there was this guy who thought his dad killed a family, except the daughter who survived since she was at a sleepover. The guy had been woken up by his dad telling him to tell the cops they had been together that night. He never forgave his dad for committing the murder and making his son cover up for him. In the end though, it turned out the son had killed the family and his dad had been trying to protect him all along. After finding this out he couldn't live with himself and the team finds his shoes (i think) on a beach and realize that he has committed suicide by swimming out as far as he could and then drowning.
Does anyone know which episode this is??