ORLANDO, Fla. -- The Operational Safety and Health Administration is investigating what went wrong after a Disney monorail crash left a cast member dead.

After speaking with experts, witnesses and Disney sources, Local 6 reporter Donald Forbes said there is a theory about what might have happened Sunday morning when a train collision killed monorail pilot Austin Wuennenberg, 21.

There are two rail lines, or beams, that run along the vast monorail system at Walt Disney World. One completes a loop around the Magic Kingdom, through the Contemporary, Grand Floridian and Polynesian hotels. The other beam runs to and from Epcot and the Transportation and Ticketing Center, which is where the accident happened.

One theory is that the pink train monorail made its final drop at the transportation center, and the operator was told to pull forward around the loop and get ready to transfer tracks onto the Magic Kingdom beam, which would have required it to go into reverse.

Meanwhile, the purple train, which had six people onboard, including Wuennenberg, was nearby at the transportation center on the Epcot beam. For some reason, the pink train did not switch tracks, so when it began to travel backward, it remained on the Epcot beam instead of moving onto the Magic Kingdom Beam.

The collision would not have happened if the collision avoidance system had been on, but it had been manually turned off, which former monorail pilots said was common practice when putting the trains away at night.

Sensors throughout the monorail system shut down the trains if they are within two train-lengths of each other, but the operator of the pink train had shut off the system, called MA-PO.

A former monorail pilot said the trains have intense spotlights located at the front and rear, and an oncoming train should have been easily spotted.