(CNN) -- A final autopsy report released Wednesday shows that Florida A&M University drum major Robert D. Champion suffered muscle damage commonly seen in such events as car accidents, prolonged seizures, child abuse and torture, an expert said.
The alleged fatal beating suffered last month by Champion, 26, during a marching band hazing must have been brutal, two experts said.
"His muscles were beaten so badly that they were destroyed like you would see in a heart attack," Dr. Howard Oliver, a forensic pathologist who is a former deputy medical examiner in the Los Angeles County Coroner's Office, told CNN after reviewing the autopsy findings.
The damaged muscles leaked out a protein called myoglobin, "and it's too much for the kidneys to process. It causes the kidneys to fail," which results in death, Oliver said.
The muscle damage is called rhabdomyolysis, Oliver said.
"Most of the time it's in (car) accidents or in people who freeze to death, and you get it in a lot of people who have prolonged seizures or in people who are in extreme physical activity like running in a marathon," Oliver said. "You see it in torture or child abuse and severe burns when the muscles get damaged."
In the case of seizures or freezing to death, people "shiver and it really works the muscles over a long period of time, and it damages them, and they release the protein," Oliver said.
Lawrence Kobilinsky, professor of forensic science at John Jay College of Criminal Justice in New York City, said the beating must have been severe.
"This kid took a real beating over his body," Kobilinsky told CNN after reviewing the autopsy report. "They're saying that the beating was so powerful, it just squashed the tissue.
"These are extremely forceful blows that this kid took, all over his back and his arms and his shoulders. It's kind of like in Egypt where they beat up that poor woman yesterday," Kobilinsky said Wednesday.
"It's interesting that there is no trauma to the neck or no trauma to the head. It's interesting that they are avoiding those areas," Kobilinsky said of the people who delivered the beating.
Added Oliver: "They just pummeled him." Had they aimed for his abdomen, "he would have bled to death."
The autopsy was performed by Associate Medical Examiner Sara H. Irrgang of Florida's District 9 Medical Examiner's Office in Orlando, with oversight from Chief Medical Examiner Jan C. Garavaglia. That office serves Orange and Osceola counties.
The complete autopsy report follows a press release issued last week by the medical examiner's office that called Champion's death a homicide. The medical examiners said in that statement that Champion died November 19 because of "hemorrhagic shock" -- the result of excessive internal bleeding -- "due to soft tissue hemorrhage, due to blunt force trauma sustained during a hazing incident."
Champion collapsed in Orlando on a bus carrying members of the Florida A&M Marching 100 band after a football game that included a halftime performance by the band.
Christopher Chestnut, the lawyer for Champion's family, has charged that Champion died after receiving "some dramatic blows, perhaps (having an) elevated heart rate" tied to "a hazing ritual" that took place on the bus.
Some band members have said Champion died after taking part in a rite of passage called "crossing Bus C." One member, who spoke on condition of anonymity, explained that students "walk from the front of the bus to the back of the bus backward while the bus is full of other band members, and you get beaten until you get to the back."
No one has been charged in Champion's death; the Orange County Sheriff's Office is investigating the case.
The medical examiner's office said last week that Champion "collapsed and died within an hour of a hazing incident during which he suffered multiple blunt trauma blows to his body."
The autopsy conducted after his death found "extensive contusions of his chest, arms, shoulder and back," as well as "evidence of crushing of areas of subcutaneous fat" -- which is the fatty tissue directly under a person's skin.
Champion didn't have any bone fractures or injuries to his internal organs.
The medical examiner didn't find any evidence of "natural disease except for a slightly enlarged heart," nor did toxicology tests reveal signs of drugs or alcohol.