Isabella Guzman, accused of fatally stabbing her mother 79 times in Aurora, sent her an e-mail the day before that said, "You will pay," according to an arrest affidavit filed Friday.

Guzman and her mother often fought, but the teenager had become "more threatening and disrespectful" toward Yun-Mi Hoy in recent days, her stepfather, Ryan Hoy, told authorities. Her mother had grown so fearful that she called Aurora police, who on Wednesday afternoon warned Guzman that her mother could kick her out of their home if she did not shape up.