On Tuesday, a medical expert said City Museum founder Bob Cassilly's death was not an accident.

It's been a little more than five years since Cassilly's body was found in the cab of a bulldozer at Cementland, a project he was working on at the time. It was ruled an accident, but family members have always suspected otherwise.

Now, an independent investigator is saying the family might be right.

Dr. Arthur H. Combs is a doctor who reviewed photographs from the autopsy for family's attorney, Al Watkins.

Combs said nearly all of his ribs were broken on both sides, which he said could not have happened in the flipping of the bulldozer, the way the crash was described at the time of his death. He said the injuries could have happened from accidents like a high-speed car crash or a fall from a significant height, but it could have also happened in a beating.

"The only plausible explanation, and my personal conclusion is that Mr. Cassilly died from a purposely beating - intentionally to death," Combs said in a statement to Watkins. "Given the location of the incident, Mr. Cassilly's age and condition and the crime scene evidence, there is no other conclusion to draw."

St. Louis Chief Medical Examiner Michel Graham gave the following statement:

“We will stick with our original findings. We feel this was an accident.”