Brianna's Killer from her Childhood takes place after The Fight Against Lauren Malloy.
Brianna's killer from her childhood (Shaun Webber) to kill Brianna and Hayley, Can Hayley, Brianna, Lloyd, Brooke, Dennis, Natalie, Caroline, Missy, Jessica, Ethan and Hayley Mitchell stop Shaun. Hayley and Brianna was best friend in Brianna's childhood when Brianna was 5 and Hayley was 8.
- Georgie Henley as Hayley McDonald
- Alexa Gerasimovich as Young Hayley McDonald
- Ellen Wroe as Brianna Albertson
- Jessica Tyler Brown as Young Brianna Albertson
- Mark Wahlberg as Shaun Webber
- Willow Shields as Chloe Albertson/Andrea and Shaun's daughter
- Amber Heard as Jessica Mitchell
- Matthew Knight as Ethan Carsia
- Chace Crawford as Lloyd McDonald
- Ryan Ochoa as Young Lloyd McDonald
- Michael Madsen as Dennis Mitchell
- J.C Brandy as Brooke McDonald
- Nick Swardson as Max McDaniel
- Marcia Jean Kurtz as Joanna Winter
- Molly Burnette as Caroline Mitchell
- Lisa Wilcox as Natalie Carmen
- Sophia Bush as Andrea Albertson
- Chloë Moretz as Young Andrea Albertson
- Caitlin Carmichael as Hayley Mitchell
- Bailee Madison as Abi Fanning
Brianna and Hayley found out they was best friend in Brianna's childhood
- Brianna: This is good.
- Hayley: Thank you after what's happening last night.
- Hayley Mitchell: Where is Chloe.?
- Brianna: I don't know.
- (Brianna, Hayley and Hayley Mitchell run to the door)
- (Chloe knock the door)
- Chloe: Mom.
- (Hayley knock the door very hard)
- Hayley: Andrea, ANDREA!
- Brianna: Andrea is not happy to see you.
- (Hayley break the door)
- Chloe: Mom.
- Hayley: ANDREA, DON'T!
- (Hayley grab the gun)
- Andrea: Get the fuck away from me.
- Brianna: But why?
- Chloe: Andrea hates you!