"He was pretty much driven from the age of 12, 13 to get in the wrestling industry," said his father, Mike Benoit. "Chris lifted weights every day. He was 13 years old ... he was breaking records in high school in our basement."
After Canadian-born Chris Benoit became a pro-wrestler at 18, his career soon skyrocketed. By age 25, he was already a world champion.
"He had won titles every place that he traveled in the world," said Mike Benoit.
While living the wrestling high life, Chris Benoit was a devoted dad and husband who cherished time with his family.
"What you saw in the ring was not the Chris Benoit on the outside," his father said. "He loved to be at home, playing with his children. That's where he wanted to be."
The Benoit Family Murders
On June 25, 2007, an unimaginable horror was discovered inside of Chris Benoit's home in Fayetteville, Ga., when police stopped by on a "welfare check" after Benoit had missed several appointments, according to the Atlanta Journal-Constitution.
Officers found his wife Nancy strangled to death and their 7-year-old son Daniel appeared to have been suffocated. Bibles were found next to their bodies. Benoit's body was found hanging from a weight machine in the basement.
"We're ruling it as a double homicide-suicide," said Fayette County Sheriff's Lt. Tommy Pope.
After seizing Benoit's computer, investigators also reported that the wrestler had searched the Internet for stories on the prophet Elijah. One of the stories of Elijah is how the prophet could raise a boy from the dead, starting with placing the dead child on his bed. Police found young Daniel on his bed.
Chris Benoit's Brain Battered
The violent deaths of the Benoit family shocked and confused everyone who knew him, especially his father.
"The next three to four days were an absolute nightmare," Mike Benoit recalled. "Watched TV 24 hours a day, waiting for someone to say something nice about my son. It wasn't happening. Everything was bad."
He was dead at age 40 and on the top of the world in his career, and Benoit's loved ones couldn't make sense of what would drive him to murder the family he cared for so much.
After hearing about the Benoit case, several researchers at the Sports Legacy Institute were eager to look at his brain. Dr. Julian Bailes, now with West Viriginia University's Health and Science Center, had been studying the brains of deceased pro-football players, and became interested in Benoit's case.
"We can only say that he had very similar changes and he had neuro-behavioral syndrome that was very similar to what we saw in others," Bailes said.
Like pro-football players who take many hits to the head, which can often lead to concussions, Mike Benoit said his son had suffered chronic blows to the head over the course of his 22 years as a wrestler -- including the six and a half years he worked for the WWE.
"Cables, ladders, chairs ... the props they were using when they were getting hit in the head. It's a real chair, it's a steel chair," Mike Benoit said.
Chris Benoit's Death and 'Roid Rage' Rumors
A media frenzy exploded in 2007 when a toxicology report showed Benoit tested positive for steroids.
Bailes is skeptical of pinning the blame of these deaths on Benoit's steroid use.
"This was a murder-suicide spree that lasted over, I believe, a three-day weekend," Bailes said. "I don't think that 'roid rage,' which is believed to be a snap judgment ... in emotions or actions, I don't think this is what explains Chris's behavior."
Desperate for more answers and disgusted with the media for painting a picture of his son as a juiced-up murderer, Benoit decided to give his son's brain to scientists for further study.
When researchers examined the wrestler's brain tissue under a microscope, they said they found evidence of years of repeated blows to the head, indicating severe brain damage.
"Chris's damage was extensive. It was replete across multiple areas of the brain," Bailes said. "It remains one the worst we have seen."
Bailes and neuro-pathologist Dr. Bennet Omalu had studied other athletes' brains before Benoit. One was former Pittsburgh Steelers Hall-of-Famer Mike Webster, who had dissolved into a shell of his former self after retiring at age 38.
After finding severe damage in Webster's brain, Omalu called the new condition "Chronic Traumatic Encephalopathy" (CTE), caused by repeated blows to the head. He plans to rename the condition, "Mike Webster's Disease."
Bailes stated that both Webster and Benoit's brains were similarly damaged, but cautioned that brain scans alone can't prove Benoit's battered brain drove him to murder.
"I think even if you had a great psychiatric input on this case that you couldn't come up with why human behavior can become so severe," he said.
Benoit was believed to have been prone to insomnia, mood swings, depression and alcohol abuse. All of these behaviors can be symptoms, doctors say, of brain damage.
After learning their findings, Mike Benoit believes that hardcore wrestling caused his son to go from being a loving, caring person to an evil one.
"I think if Chris Benoit had been anything other than a professional wrestler ... he would still be alive," he said.
The WWE vehemently disagreed with this position and questioned the scientific findings on Benoit.
In a statement to ABC News, they said Benoit's claim that head trauma could be the "cause of his son's aberrant, criminal behavior ... is impossible." Click here to read the full statement.
WWE argued if he was suffering from extensive brain damage, he would not have been able to function as a pro-wrestler, "much less commit a methodical murder-suicide over a 48-hour period."
Mike Benoit continues to defend his belief about his son's death and denies that he's using brain damage as an excuse for the murder-suicide.
"I would like people to have an understanding that the tragedy that took place in 2007 happened because of his career choice," he said.
Watch the full story tonight on "Secrets of Your Mind" at 10 p.m. ET.
World Wrestling Entertainment (WWE) Full Statement to ABC News
"It is natural that a father would try to come up with a reason why his son would tragically murder his wife and child, and then commit suicide. Based on the study by the Sports Legacy Institute that claimed Chris Benoit had the brain of an 85-year-old with dementia, Mr. Benoit asserts that head trauma was the cause of his son's aberrant, criminal behavior. However, common sense would dictate that this is impossible. Someone with the brain of an 85-year-old with dementia would be unable to keep a traveling work schedule, drive himself to arenas, and perform intricate maneuvers in the ring much less commit a methodical murder-suicide over a 48 hour period."