A University of Florida pre-med student drove to his mother’s house and stabbed her to death, reportedly telling authorities he did it because “she got on my nerves.”

Emmanuel Espinoza, 22, called 911 and confessed to killing his mother, Elvia Espinoza, 46, immediately after attacking her, Polk County Florida Sheriff Grady Judd said in a video update. Emmanuel Espinoza is being held in jail and will be charged with first-degree murder, Judd said.

The suspect, who is a student at the university’s campus in Gainesville, Fla., was traveling to Frostproof on Friday for a family event. He called his mother and asked for permission to stay at her home, Judd said.

Emmanuel Espinoza arrived at about 2 p.m. and knocked on the door, Judd said. When his mother opened the door, he immediately began stabbing her, Judd said.

Elvia Espinoza, who was on the phone with a family member when the attack occurred, tried to run but her son stabbed her “many, many times” until she fell and died, Judd said.

Judd said the suspect told investigators that he decided to kill his mother during the drive to her home.

“He said, You know, I had wanted to kill my mother for many, many years because she got on my nerves,” Judd said. Judd said that when the suspect was asked to describe his relationship with his mother, he said “about an eight out of 10, that he really loved her, but she irritated him.”

“This is a horrible event,” Judd said. “Mom is a second-grade teacher at Ben Hill Griffin Elementary in Frostproof, Florida, and is well-loved by the community. It’s a very sad day with an inexplicable, vicious murder.”