The driver underwent surgery for a compound fracture to his left arm. He was in critical condition Thursday night.
The bus was less than two miles away from its destination, the Tropicana Casino and Resort, when it crashed.
"He went through the windshield, and at this point, we've got a ghost driver, with the bus continuing on without anyone at the wheel," said Sgt. Monica McMenamin, a police department spokeswoman. "The bus continued on and drove over him."
The crash happened shortly before 11:30 a.m. on Route 40, known locally as the Black Horse Pike, one of three main entranceways to the nation's second-largest gambling market.
Police said the bus was unable to stop as it approached traffic stopped at a traffic light at the bottom of a curving bridge over the Great Thorofare, a shallow waterway about a half mile from the beach. It was not immediately clear why the driver was unable to stop.
"There was traffic stopped in front of him and he realized he was having issues stopping the bus," police Capt. Joseph Nolan said.
One other person was initially listed in critical condition, but was later upgraded.
Police said the bus struck two vehicles, then swerved to avoid trying to hit others and smashed into a retaining wall that prevented it from splashing into the water.
"At this time, the bus driver was ejected from the vehicle," said police Lt. Charles Love. It was not immediately clear if the bus driver was wearing a seat belt.
The bus windshield was smashed out and its front grill and bumper were gone. Its front passenger door was mangled and hanging off the side.
In addition to those most seriously injured, 22 others were taken to hospitals. Hospital officials would not release information on their injuries, but a hospital spokeswoman said some had been released by late afternoon. Uninjured passengers were taken to the Tropicana Casino and Resort.
The bus is owned by Sun Lee Bus Co. of New York City and was carrying passengers from Chinatown, police said.
The accident occurred shortly before 11:30 a.m. on eastbound Route 40, known locally as Albany Avenue, on the outskirts of the city.
Sgt. Stephen Jones, a New Jersey State Police spokesman, said state inspectors would examine the bus to see if a mechanical defect may have contributed to the accident.
