LIBERTY, MO - It's been more than four years since a deadly school bus crash in Liberty, and now investigators say that the verdict is in -- it was driver error.

Investigators from the National Transportation Safety Board have looked at what happened on the corner of 152 and 291 Highways. On Tuesday, they said that investigation uncovered that pedal misapplication, or hitting the gas instead of the brakes, may have played a role.

The crash killed two men who were both sitting at a light: attorney David Gleason and advertising agency president David Sandweiss. In addition, 47 of the 53 students on the bus were injured in the wreck.

The investigation includes new pictures, some closer than you've seen, from the scene on May 5, 2005. (You can view more evidence from the investigation here)

Now, many parents and a local state representative are pushing for new rules regarding the design of school busses, and to make seatbelts mandatory on Missouri school busses.

"I still, every now and then, think about it when we go through that intersection. Yeah. It was pretty horrible," parent Evan Bernstein said.

The Bernsteins' three kids are too young to have been involved in the wreck. Next year their oldest starts kindergarden. While the Liberty crash isn't the main reason, Bernstein says he'll probably drive his son himself.

"And you know, you see things like that happen and it just scares you to death, you know, because your child isn't under your control at that point," Bernstein said.

John Sprugel's seven-year-old son was on the bus that afternoon.

"(He Suffred) just some minor bumps and bruises," said Sprugel. "A lot of it was more emotional than anything else."

Sprugel says that he supports rules that would force school bus makers to redesign the size and shape of gas and brake pedals to avoid the confusion that investigators say happened in the Liberty accident.

"You could see where somebody could, if thought they were on the brake instead of the gas, see where somebody might be able to panic," said Sprugel.

The report also includes eye-witness accounts of the accident.

"It was flying, it was really moving," one witness said.

"I heard the crash from behind me and looked to the right real fast and I saw the bus flying through the intersection and hit the red car in the side," another said.

The crash killed two fathers who were both sitting at a light: attorney David Gleason and advertising agency president David Sandweiss.

Bus driver Denise Thomas had no comment.

Missouri State Rep. Tim Flook, a Republican from Liberty, says that while pedal misapplication may be the cause of this accident, he says that federal investigators ignored the fact that accidents still happen. He has filed a bill mandatig lap and shoulder seat belts on school busses to reduce injuries in an accident.

"They're looking soley at the cause of the accident and whose fault it wa,s but I really think they need to go a step further and look at injury prevention," said Flook. "That's the distinction about lap shoulder seat belts. If you invest in those the injury prevention improves considerably, particularly whenever you have a roll-over of any sort."

So far, only seven states nationwide require school busses to have seat belts. Missouri and Kansas are not among them.

A year and a half ago, a Clay County grand jury declined to indict Thomas on any criminal charges. Liberty School District confirmed that Thomas twice pointed out brake problems in the months before the crash.

On Tuesday, Thomas' attorney told FOX 4 that she still insists that there was a mechanical failure despite the NTSB's findings.

But as for Sprugel, he says that he wants to make sure it doesn't happen again.

I never, ever want to have to go upon a scene like that again," said Sprugel.