Surveillance video shows Troy Fischer, 43, punching a man 18 times before dragging him off the bus and leaving him on the side of the road.
The video of the incident which took place on March 23 was released Friday by officials in Lincoln.
Mike Esposito, director for the city's Public Works and Utilities Department, said the March incident began after Fischer notified his supervisor that was having trouble with a passenger. The supervisor instructed Fischer to let the passenger leave voluntarily or call police.
"His directions were blatantly ignored," Esposito said. "He took matters into his own hands."
Fischer reportedly begged his boss to erase the surveillance tape. StarTran Bus Service officials, however, fired him and turned the tape over to authorities.
The Associated Press contributed to this report.