GLENVIEW, Ill. (WTVO) — An Illinois man was arrested on Monday after stabbing his dad to death in a fight over marijuana.

Isaac Thurston, 20, has been charged with First Degree Murder in the death of Perron Thurston, 50, according to the Glenview Police Department.

Officers responded to a home in the 110 block of Arbor Lane around 6:36 a.m. for reports of a stabbing during a domestic incident. Perron was transported to a local hospital where he was pronounced dead.

Isaac reportedly told police “I am a murderer” when he was taken into custody, according to court records as reported by The Kansas City Star.

Perron had reportedly been upset about Isaac’s marijuana use, saying that he should not work since he had been smoking. Isaac grabbed a knife from the kitchen as the argument continued and stabbed Perron in the torso.

“I don’t know why I did it,” he told officers, according to court records.