CHICAGO (CBS) — The Chicago Office of Emergency Management and Communications has released the 911 tapes from a horrifying attack this month, in which four teenagers disabled a CTA bus and beat and robbed a passenger.

The teens – two of them 17 years old and two of them 13 – got on the bus in the 600 block of East 71st Street around 7 p.m. Jan. 21.

They disabled the engine by hitting a switch on the side of the bus, then began beating and punching the passenger, a Chicago Transit Authority spokesman told CBS 2.

In a 911 call, a woman on the bus is frantic.

“A group of guys, they… oh my God… they got on the bus and started beating on people, trying to rob everybody on the bus,” the woman said.

Following the incident, Grand Crossing District tactical unit officers responded immediately to the call and arrested two of the teens at the scene, police spokesman John Mirabelli said. Two others attempted to flee the area but were soon caught by police.

A witness on the bus, along with the victim, were able to identify the four as the offenders, Mirabelli said.

The two 13-year-olds have each been charged as juveniles with a count of misdemeanor battery.

anthony williams darius love 0122 Rider: Teens Got On The Bus And Started Beating On People

Anthony Williams (left) and Darius Love (right), both 17, were charged with beating a CTA bus driver on Jan. 21, 2012. Two 13-year-old boys were also charged as juveniles in the attack. (Credit: Chicago Police Department)

The other two, Darius Love and Anthony Williams, both 17, were charged as adults. Love, of the 700 block of East 90th Place, has been charged with a misdemeanor count of battery and a felony count of robbery. Williams, of the 7200 block of South Evans Avenue, stands charged with a misdemeanor count of battery and a felony count of attempted robbery.

The Sun-Times Media Wire contributed to this report.