An 18-year-old Olney man has been charged with attempted murder in a choking attack that left his 7-year-old sister in extremely critical condition, Philadelphia police said Wednesday.

Simere Alford was taken into custody after he was found about 11:20 Wednesday morning in the back seat of a police car at the 35th District, Broad Street and Champlost Avenue, said Capt. Mark Burgmann, commanding officer of the Special Victims Unit.

"When officers found him in there, he said he did something stupid," Burgmann told reporters during a news conference.

Alford had apparently entered the unlocked patrol car to surrender, Burgmann said, adding that the suspect's mother had told police she had been having problems with her son recently. She said she believed he had been smoking a synthetic marijuana known as K2.

She found her daughter unresponsive and with a plastic bag on her face in the basement of the family home in the 5500 block of North American Street shortly after she called police about 1:10 a.m. to report that Alford had stolen her SUV and was high on drugs.

The mother was looking for her vehicle registration when her 14-year-old son noticed that his younger sister was not in bed, Burgmann said. The family began a search of the house and the mother found her daughter in the basement.

Police performed CPR on the girl and rushed her to Einstein Medical Center, where she was revived and afterward transferred to St. Christopher's Hospital for Children. The staff there put her on life support.

The mother told police that she had come home around 10 p.m. Tuesday and that nothing appeared amiss. Alford was using his phone and the girl was asleep in her second-floor bedroom.

At some time after midnight, Alford barged into his mother's bedroom and demanded her car keys, Burgmann said. He left the room and then returned and took his mother's pocketbook. He then fled in her Mitsubishi Montero.

The Montero was found at Champlost and Third Street 10 minutes after the mother's first call to police. The vehicle had been abandoned after crashing into several cars, Burgmann said.

Alford was charged with attempted murder, aggravated assault, simple assault, recklessly endangering another person, theft, receiving stolen property, and robbery of a motor vehicle. Burgmann said there was no preliminary evidence that the girl was sexually assaulted.

Alford was being processed by police Wednesday night, and bail had not been set.