LAKE BUENA VISTA, Fla. -- The monorail at Walt Disney World reopened to guests on Monday, a day after a train operator was killed in the first fatal accident in the 38-year history of the park's transportation system.

Austin Wuennenberg, a monorail operator, was pronounced dead at the scene after two monorails crashed at about 2 a.m. Sunday at the Ticket and Transportation Center near Magic Kingdom.

The Medical Examiner's Office on Monday said Wuennenberg died from multiple traumatic injuries. His death was ruled accidental, officials said.

"The Occupational Safety and Health Administration has released the Walt Disney World Monorail system back to us and we have completed a thorough safety inspection and system checks to verify that it is safe to operate for our guests and cast," a Disney official said.

The federal agency's full investigation into whether workplace safety rules were broken could take up to six months.

The National Transportation Safety Board will also investigate the incident.

Three 911 calls made just after the crash were released Monday morning.

"We just heard a loud bang and my manager came running in to tell me to call you," a caller told a dispatcher when describing the incident.

"A monorail was waiting to come into the station, I believe, or did not leave the station and the other one cleared the station and it was a head-on collision," another caller told the dispatcher.

A former monorail pilot spoke with Local 6 about the safety measures on the monorail trains.

"Purple would have been doing what he was told to do and he wouldn’t have been going fast," the former monorail pilot said. "In order for that train, the blue train, to get close to that red train, you've got to override the safety system, basically."

The former pilot said the monorail is equipped with a high-tech anti-collision system that is supposed to automatically stop the trains when they get within 500 feet of each other, but it is typically deactivated at the end of the night as the monorails are being put into storage. She said the trains are also equipped with an emergency kill switch that can be pulled at any moment by a pilot or manager.

"Monorail Central is the one, basically, the main person who should have been hitting it (the kill switch) if these two drivers did not see what was coming, because you're supposed to be standing right there within a foot of that kill switch button, basically," the former pilot said.

The operator of the other monorail was not injured, although he was emotionally shaken and transported to a nearby hospital. At least five other people were evaluated after the crash, but no other injuries were reported.

According to witnesses, a monorail was returning from Epcot when it slammed into the rear of the other train.

"We heard a loud explosion, and you could hear things falling to the floor. We ran to see what it was, and we saw the monorails collided," a witness said.

"To see the accident, to see the scene of what had happened and the fact that there was a life that was lost, it was very sad. It was very somber," said Bo Jones, deputy chief for Reedy Creek Fire Department.

Video obtained exclusively by Local 6 News shows guests trying to help the driver who was killed in the crash. The video was recorded by a person who was at the scene when the crash occurred.

"Is there somebody in here?" a person asked. "Can you hear us? Hey, can you hear me? Can you hear me?"

The cause of the crash is not known, and the Orange County Sheriff's Office has launched an investigation into the fatal holiday accident.

Wuennenberg was a computer science major at Stetson University and was set to graduate in 2010. Wuennenberg, who graduated from Celebration High School in 2006, served as a teacher's aide from August 2007 to May 2008, according to his Facebook page.

Wuennenberg listed his position as "Monorail Pilot," a role he had held since October. He described his job as "running the highway in the sky!" The Facebook page also stated that Wuennenberg worked at Disney in "Sunset Attractions" from June 2006 to September 2008. His interests included video games, computers, programming and comedy.

Wuennenberg's family issued a statement Sunday night.

"Austin Wuennenberg was a senior at Stetson University, studying computer science. He always enjoyed his work at Disney, and especially enjoyed his work as a monorail pilot. He has many great friends whom he has positively influenced; everyone will truly miss this dynamic young man. Austin's family would like to thank friends and well-wishers for their kind thoughts and prayers. We appreciate sensitivity and respect from the media during this difficult time."

Walt Disney World Vice President of Public Affairs Mike Griffin issued a statement on Sunday, offering condolences to the employee's family.

"Today, we mourn the loss of a fellow cast member. Our hearts go out to the family and fellow cast members who lost a co-worker and a friend. Safety of our guests and cast members is our top priority. We will work with law enforcement to determine what happened," Griffin said in the statement.

Griffin would not comment on the circumstances surrounding the crash.

"They are extremely rare," Griffin said of accidents at the park. "The safety of our guests and cast are a top priority above all else."

Stay with Local 6 News and ClickOrlando.com for more information about the crash.