"I'm sure he's greatly sorry for what did happen," Jackson told WABC-TV.
They said Williams is known for his courage.
"Years ago he ran into a burning building and saved a family, there was a girl, a grandmother in a wheelchair, he brought them out the fire," Bookard told WABC-TV.
"Our -- and the entire city's -- prayers, thoughts and sympathies are with the victims, and their families and loved ones," said New York City Mayor Michael Bloomberg in a statement.
The mayor said that the New York State Police is leading the investigation into the accident, and that city agencies have set up a Family Assistance Center to provide family members with information regarding their loved ones.
"People were saying, 'Oh my God. Oh my God,' holding their hands on their heads," limo driver Homer Martinez told The Associated Press about the carnage at the scene of the accident. "I saw people telling other people not to go there, 'You don't want to see this.'"
New York firefighters and medics were quickly on the scene, supporting the bus with wood planks.
"As we back through the bus we found more people pinned because of the stanchion," FDNY Chief of Department Edward Kilduff told the New York Daily News. "We had about seven or eight people pinned in the rear of the bus that we had to actually cut out by removing seats or cut a hole in the roof of the bus."
The bus was en route from Mohegan Sun casino in Connecticut to lower Manhattan's Chinatown.
"Our heartfelt sympathy goes out to the families of all those involved in this morning's tragic bus accident in New York, " Mohegan Sun chairman Bruce "Two Dogs" Bozsum and president Jeff Hartmann said in a statement Saturday.
WABC News' Mark Crudele, ABC News' Sherisse Pham, and The Associated Press contributed to this report.