A Spotsylvania County teenager charged with fatally stabbing his mother did so after taking LSD for the first time and watching an animated cartoon in which the main character talks about killing his mom, according to one account.

Matthew Charles Robertson, 18, is charged with second-degree murder, using a knife in commission of a felony and malicious wounding in the Saturday morning slaying of Susan Leaf Robertson.

The 61-year-old mother of seven was stabbed several times in the bedroom of her home in Salem Fields subdivision.

Robertson’s husband, Neal, also was attacked, as was a 16-year-old friend of Matthew’s who recounted the incident to his mother.

Michelle Kurz said her son told her he and Matthew Robertson were watching TV in the Robertsons’ basement Saturday night.

The two teens stayed up watching the animated program “Family Guy,” in which a boy named Stewie frequently talks about killing his mother, Kurz said.

The two began taking LSD and Kurz said her son, who also was injured, doesn’t remember much about how the attacks occurred.

The Free Lance–Star is not identifying Kurz’s son because of his age. He has a different last name than his mother.

Lt. Col. Michael Timm of the Spotsylvania Sheriff’s Office said there was a big-screen TV in the room where the teens were, but he did not know what they might have been watching.

Robertson is being held without bond in the Rappahannock Regional Jail. A judge Monday ordered a competency exam for him and scheduled a preliminary hearing for April 6.

Kurz said her son sustained a wound to his head, a split lip, a broken nose and bruises on his back. But she said her son is worried more about his friend than himself.

Kurz, who lives near Augusta, W.Va., recalled her son and Matthew Robertson visiting her for three weeks in the summer of 2009. Her son lives with his father in Spotsylvania.