An 18-year-old from Aurora, Colo., sent her mother an email that said, "You will pay" the day before she stabbed the woman 79 times, an arrest affidavit filed Friday revealed.

Isabella Guzman and her mom, 47-year-old Yun-Mi Hoy, often fought, but her stepfather, Ryan Hoy, told authorities that the teen had recently become more "threatening and disrespectful." His worried wife showed him an email from Isabella on Wednesday morning that said, "You will pay," and she later called the police saying that her daughter "had threatened to harm her," Denver's 7NEWS reported.

Ryan Hoy told police he heard a thumping sounds coming from upstairs while he was eating dinner on Wednesday night. He also heard his wife, who was taking a shower, calling his name, so he rushed upstairs and tried to push his way into the bathroom. He could still hear the shower running, and saw Isabella before the teenager shut and locked the door.

Yun-Mi Hoy was stabbed 79 times in the face and neck in her home in Aurora, Colo., on Wednesday night, police said.

The man said he saw blood coming out the bottom of the door and ran to call 911. He returned to the bathroom door with his cell phone, and then saw Isabella walk out holding a knife. She was silent and stared straight ahead as she passed him, Ryan Hoy said.

According to the affidavit, Ryan Hoy said he found his wife's naked and bloody body on the floor of the bathroom. She was on top of a baseball bat and her throat had been slashed. Yun-Mi Hoy was pronounced dead on the scene.

Isabella's father, Robert Guzman, told The Denver Post that the teen had spit in her mother's face on Tuesday, the night before the killing.

The 18-year-old was reportedly becoming more "threatening and disrespectful" toward her mother.

He told 7NEWS that he had a talk with his daughter about respect, at his wife's request, just hours before the slaying.

An autopsy showed that Hoy died after being stabbed repeatedly in the neck and face.

On Friday, an Arapahoe County judge ordered that Isabella remain jailed without bond on suspicion of first-degree murder, according to The Denver Post.