What happened the last night Lily and Atlas were together when they were teens?

The last night that Lily and Atlas were together when they were teens, she did not think to lock her bedroom door. Her father heard her talking to someone and barged into her bedroom. When he saw Atlas in bed with her, he took a baseball bat and beat Atlas. Someone called the police. When the police arrived and pulled her father off from Atlas, Atlas was unrecognizable. They had to take Atlas away in an ambulance. They also had to take Lily in another ambulance because she had a panic attack and could not breathe.