(CNN) -- Two monorail trains at Walt Disney World collided early Sunday, killing a 21-year-old driver.

A witness said one of the trains rammed into the back of a stationary train about 2 a.m. at the resort's Ticket and Transport Center.

There were eight people on board at the time, the Orange County Sheriff's Office said.

A second employee was taken to a hospital to be checked; the six guests -- members of a single family -- were evaluated by paramedics at the scene and released. Disney World officials said none of the seven was injured.

Authorities identified the driver as Austin Wuennenberg. According to his page on LinkedIn.com, the Stetson University student expected to graduate in 2010.

"It's a terrible day for us," said Mike Griffin, Disney's vice president for public affairs. "Our hearts go out to to Austin and his family."

The theme park is working with county authorities and the U.S. Occupational Safety and Health Administration in the investigation.

"The safety of our cast and our guests is legendary and it's our top priority," Griffin said. Disney World calls its employees "cast members."

The monorail was shut after the accident, Griffin said.

Images from the scene showed the front car of a train badly damaged where it hit the other train at a station.