When an FBI agent realized a teenager had snuck behind the wheel of the SUV the agent had left running at a West Side gas station early Monday morning, he tried to let the boy know he picked the wrong car to steal.

“I’m the police! I’m the police!” the agent said. “You don’t want to do this.”

Still the boy sped off, dragging the agent about a half a block and injuring the agent’s right arm, hip and back before getting away in the 2014 Chevrolet Equinox. That’s according to a prosecutor who described the theft during a Wednesday hearing in Cook County Juvenile Court.

The boy, who was already on probation, has a lengthy juvenile court record. He has previously been found guilty of aggravated unlawful use of a weapon and possession of a stolen car.

Cook County Judge Marianne Jackson ordered him held in custody while he faces the new charges of vehicular hijacking, aggravated possession of a stolen motor vehicle, possession of a stolen motor vehicle and aggravated battery to a peace officer.

Chicago police announced the charges against him Tuesday night and identified him only as a 17-year-old male, because he has been charged as a juvenile.

The 32-year-old FBI agent had left the Equinox “momentarily unattended with the engine running” at 12:10 a.m. Monday at the gas station in the 300 block of South Morgan, authorities have said. That’s when the boy jumped inside and took off after the agent confronted him.

Firearms and tactical gear, including a ballistic vest, were in the car. An FBI spokesman would not say precisely how many or what type of weapons were inside, and he declined to say Wednesday whether they had been recovered. In court, a prosecutor only mentioned a radio and tactical equipment.

The SUV was discovered at 7:21 p.m. Monday in the 900 block of South Leavitt, a few blocks from the FBI’s Chicago headquarters. The boy was taken into custody about 10:15 a.m. Tuesday.