Four people were killed and over 30 others were hurt when a freight train hit a charter bus in Biloxi, Mississippi, on Tuesday, authorities said.  The accident happened shortly after 2 p.m. local time (3 p.m. ET). Around 50 people were on the bus, which was traveling from Austin, Texas, Police Chief John Miller said.

Thirty-five people have been transported to hospitals, Biloxi Fire Chief Joe Boney said.  “It’s a terrible, chaotic scene,” Miller said. “We’re not sure about the bus itself, why it was stopped, if it was having engine problems or what,” he said.

A witness described hearing the train continuously blow its whistle before it struck the bus — normally trains give two short horn warnings. The impact threw people from the bus, David Mc Donald, who works at a nearby car service shop, told NBC News.

“Bodies come flying out of the bus, they went over the top of the bus, under the bus, under the train … I mean, it’s just horrific,” Mc Donald said in a phone interview. “I just thank the Lord that as many people that was on that bus, that the amount of survivors that there are,” he said.

The bus was on the tracks at Main Street when it was struck by the eastbound train, Miller said.

The private charter bus was carrying people from Hollywood Gulf Coast Casino in Bay St. Louis to the Boomtown Biloxi Casino, the casino company’s regional director of operations said in a statement.  “Our thoughts and prayers are with the families of those who tragically lost their lives and all those affected by this accident,” Ameet Patel, senior vice president of regional operations for casino owner Penn National Gaming, said.

The National Transportation Safety Board said it was aware of the crash and monitoring information.

The train pushed the charter bus approximately 300 feet down the tracks, Biloxi city spokesman Vincent Creel told the Biloxi Sun Herald newspaper.

Witnesses told the newspaper the bus became stuck on the tracks.  “Maybe it was about 5 or 10 minutes before the train arrived at that intersection,” Mark Robinson told the newspaper. “He was blowing his horn and doing all kinds of different things trying to get the bus off the tracks, but it got stuck.”

A spokesman for railroad company CSX said the mixed freight train was traveling from New Orleans to Mobile, Alabama, and had three locomotives and 52 cars, 27 of which were loaded. No one on the train was hurt.

“Our thoughts are with all involved,” CSX spokesman Gary Sease said. The bus is owned by Echo Transportation, authorities said. Echo Transportation President and CEO John Ferrari said the company was in touch with authorities.