Mystery unsolved about what happened in deadly school bus crash

DENVER -- There's still a mystery about what exactly happened during Sunday afternoon’s horrific bus crash at the Denver International Airport. Many are asking why the bus driver missed the turn and slammed right into a concrete pillar.

Was it a medical emergency, inexperience driving a bus at the airport or something else? Even some of the most seasoned travelers said Monday they have trouble navigating DIA at times.

“Generally, I find airports are confusing places to drive regardless of where you are," said Debra Ciskey, who travels often for work.

“I'll be driving, and I'll be like, ‘Oh, where am I going?’ I’m always calling someone,” said frequent flyer Tiffany Lewis.

The bus driver in the crash, Kari Chopper, had already picked up the students, but for some unknown reason was returning to DIA’s East Terminal.

She took the on-ramp to Level 4, but instead of making the turn, barreled right into a concrete pillar.

If she had kept going, less than 50 yards later, she would not have had the clearance to get into Level 4. It's only 9 feet, 6 inches, so the roof of the bus would have hit the floor for Level 5.

An airport spokesman said Monday that drivers have three opportunities to turn around before getting to Level 4. And, he said, the airport's signs are "abundantly clear."

While that may be true, some frequent flyers say DIA can be confusing and could be more clearly marked.

“I think it could be,” said Ciskey. “They could have different colors. All the signs are blue and white. And so, if they had different colors for different areas, that could help.”

The investigation into the crash will likely take several weeks or even months to complete, as police have to look into Chopper's medical history and driver's record, bus maintenance records and more to find out exactly what happened.

"I think it might be 2 or 3 months before we get a final result," said safety consultant Chett Winchell.

The superintendent of the district, Chris Gdowski, issued a letter to staff and families Monday thanking the community for their thoughts and prayers.