My imagination of this seriouse crossover connected story. I can't confirm this story as true. Angela can, this is just my imagination.

The five dead children were Angela and Wheatley's bullies, specifically the one that possesed Freddy. They thought it was funny but they didn't think it hurt the twins. Afton (Purple guy) killed the children because he was tired of them hurting his son and daughter. Later he realises that they were still children he murdered and is afraid for his kids. "I can't afford to lose them. To anyone or myself." Later, he learns about the animatronics killing the nightguards and knows that the children have possesed the robots. Wheatley comes to hus dad and shows the diary entry about the murder. Afton explains to the two how he lost control during the murder. He tells them to stay home. If he isn't back before their birthdays then they have to go to the givven adress which leads to Carolin Jonson's house. There is a seperation between the kids. Wheatley goes to Aperture and Angela ends up in the underground while Afton gets put in the springtrap suit.

Again...just my imagination.