A man from Tennessee is facing serious charges of attempted murder, aggravated assault, and arson following an incident where he allegedly set his grandmother on fire.

According to an arrest report, a witness detained 39-year-old Christopher Medula until law enforcement officers arrived, as reported by WRCB.

The victim was airlifted to a Nashville hospital, suffering burns that covered 70 percent of her body.

The incident occurred on Tuesday in Soddy-Daisy, according to the report. Medula is accused of pouring gasoline over the woman and igniting it with a lighter before attempting to escape. However, the witness held Medula at gunpoint to prevent his departure.

WZTV reported that Medula allegedly told the witness that he “had to do it” because he believed his grandmother was “the devil.”

Deputies said the grandmother was still conscious when they arrived, with severe burns and gasping for breath.

“Chris did it,” she told them. “He poured gas on me. He’s lost it.”

The report said the witness saw Medula trying to hold the door to the camper shut while the woman desperatedly tried to get out. When deputies arrived, they found her lying on the ground outside.

The grandmother is in critical condition in Nashville’s Tristar Skyline Medical Center. She has been removed from life support, the station said.