A Philadelphia man has been arrested for allegedly attempting to kill his 7-year-old sister, who now is on life support and could be brain dead, WPVI-TV reports.

The mother of the girl found her unconscious early Wednesday morning in the family’s basement with a bag over her head.

According to police, Simere Alford, 18, allegedly tried to suffocate or strangle the girl.

Prosecutors charged Alford on Wednesday with a litany of crimes, including attempted murder, aggravated assault and recklessly endangering another person, The Philadelphia Inquirer reports.

Police found Alford Wednesday morning locked in the back of a police car in an apparent attempt to surrender. He told officers at the time that he “did something stupid,” said Capt. Mark Burgmann of the Philadelphia Police Department.

The mother told police that everything was OK on Tuesday night when she arrived home around 10 p.m. The girl had been sleeping in her bedroom and Alford was on his phone, the Inquirer reports.

But the mother called police shortly after 1 a.m. Wednesday to report that she believed her son had stolen her car and that he was high on synthetic marijuana.

While police were at the residence, the mother’s 14-year-old son said the 7-year-old girl was missing, which prompted a search of the home, WPVI-TV reports.

The mother later found the girl on the basement floor with a plastic bag on her face. Officers attempted CPR and then rushed the girl in the back of a squad car to a hospital, WPVI-TV reports.

The girl’s father told the television station that she could be brain dead.

Bail for Alford had not yet been set Wednesday night.