Four people were injured early Saturday morning after a group of teenagers shot an AC Transit bus after it dropped them off in Oakland.

Witnesses reported no problems with the teens when they were aboard the bus, but when the teens got off at 55th Ave and International Blvd a little after midnight, they started firing at the back of the vehicle as it was taking off.

The entire rear window was blown out, and there were bullet holes in the bus’ engine.

Passengers say that at the time of the shooting, the bus was driving at full speed. But when back window exploded, the driver slammed on the brakes and reportedly sent passengers, who had fallen to the floor, tumbling to the front of the vehicle.

When the driver realized everyone was in danger, he sped away and pressed the emergency alarm.

The bus kept driving on International Blvd. until police caught up with it around 13th Ave.

"The driver responded appropriately," said Alameda County Sheriff Sgt. J.D. Nelson. "He stepped on the gas and got the bus out of there, which is exactly what he should do."

None of the passengers on board were shot, but officers on scene said four people were injured during the sudden movements of the bus. They were taken by ambulance to a nearby hospital with non-life threatening injuries. As of later that morning, there were no updates on their conditions.

No arrests had been made in the case as of Saturday. Officers on scene told KTVU that they had no reason for the shooting, as there were no arguments prior to the incident.

AC transit said its buses have between six and eight cameras recording in and outside the vehicle, and that it did get surveillance video from the bus that was hit.    

Investigators will also check businesses near the attack for clues from their security systems.  

On occasion, and on certain routes, deputies have been assigned to tail buses to prevent robberies, but this gunplay seemed completely random.

“Obviously if someone wants to do something as stupid as this, we want to get them into custody,” Nelson said.

A spokesman for AC Transit said the bus that was struck was drivable except for the shattered window, which would be quickly replaced and that it's probably back on the road already.