The CTA driver walks briskly down the bus aisle, his voice calm and firm as he keeps saying, "Break it up, break it up."



In a public transit system as large as Chicago’s, scuffles break out from time to time, and the first few seconds of the one captured on a cell phone video last Thursday are pretty routine. But what happens next isn't.



“We got a weapon here?” the driver asks, bending down and picking up a handgun from the floor. “On no, we ain’t going to have this. We ain’t going to have this. I need to call the cops now.”



As he walks back to the front of the bus, gun in his hand, the driver remains composed as he shoos the apparent owner of the gun off his bus.



"You better go, you better go," he says, "We ain't going to have this. . .Get your stuff, get your stuff. You better go."



By this time, the police have arrived and begin chasing the youth as he steps from the bus.



The video was shot by a passenger who later posted it to a public Facebook group that collects anecdotes from CTA riders.



“Holy s---,” says the narrator of the video. “He had a gun?”



CTA spokeswoman Catherine Hosinski confirmed the incident and said it was under investigation. She said the agency would have no further comment on the driver's actions.



Chicago police are working with the CTA, according to Police News Affairs Officer Jose Estrada said.