Mel Farr played seven seasons for the Detroit Lions and was a successful businessman before his death in 2015 at age 70. His daughter Monet and son Mike join OTL to discuss their father's heath in his later years. (5:47)

Former Detroit Lions running back Mel Farr, who once also headed the nation's largest black-owned business, had Stage 3 chronic traumatic encephalopathy (CTE) at the time of his death in 2015, Outside The Lines has learned.

Farr died suddenly on Aug. 3, 2015, at his home in Detroit from a massive heart attack due to undiagnosed hypertension. He was 70.

After his death, Farr's family donated his brain and spinal cord to Boston University School of Medicine where, since 2008, researchers have been testing the brains of deceased athletes for the presence of CTE, the progressive degenerative brain disease associated with repeated blows to the head.

CTE can only be confirmed with certainty after someone dies. Symptoms include memory loss, confusion, impaired judgment, impulse control problems, aggression, depression and, eventually, progressive dementia.

Former Lions running back Mel Farr had Stage 3 CTE at the time of his death in 2015, OTL has learned. AP Photo/Preston Stroup

"Mr. Farr had Stage 3 CTE, which is consistent with other football players of similar age and exposure," said Dr. Ann McKee, the director of Boston University's CTE Center. "At Stage 3, the disease is widespread, but most severe in the frontal lobes as well as the medial temporal lobes, specifically the hippocampus, which plays a critical role in forming new memories, and the amygdala, which governs emotion.

"Mr. Farr had symptoms consistent with other Stage 3 cases, including memory problems, significant personality change, and behavioral symptoms," added Dr. McKee, who is also a professor of neurology and pathology at the Boston University School of Medicine and the Chief of Neuropathology for the VA Boston Healthcare System. "His family noted that Mr. Farr was aware of, and frustrated by, his decline."

Said Farr's daughter, Monet Bartell: "My dad for some time had been suffering. He was losing his memory. Things he should remember, he couldn't remember."

Farr, who was a 1967 first-round draft pick and NFL rookie of the year, played for the Lions from 1967 to 1973. He played college football at UCLA and high school football in his hometown of Beaumont, Texas. In total, he played the game for 18 years. His family's story will be part of an Outside The Lines special, "Football Forever" (Saturday, 10 p.m. ET, ESPN).

According to Dr. McKee, the latest research from Boston University finds that "CTE risk, both the presence and severity, is associated with number of years playing football."

Before his death, Farr suspected he had CTE. He, along with his brother, Miller Farr, his cousin Jerry LeVias and two sons, Mel Farr Jr. and Mike Farr -- all former NFL players -- joined a still pending class-action lawsuit against the league claiming the NFL hid known concussion risks from players.

"We were never told the lifelong effects of the multiple jarring hits in the NFL," Mike Farr said.

Mel Farr, with his wife Jasmine, in one of the last photos taken of the former Lions running back before his death in 2015. Jasmine Farr

"What we called it back then was 'getting your bell rung'. What they may call it now may be a mild concussion," Mel Farr Jr. said. "If you took a hard hit, you got up, you were a little woozy, 'Oh, he just got his bell rung' -- you were able to go back to the huddle."

While his family was not surprised by the CTE diagnosis, they were surprised that Farr had Stage 3, which is usually marked with aggressive behavior and more cognitive impairment than what Farr seemed to display. At Stage 4, there's usually a clinical diagnosis of dementia.

Bartell said a doctor told her that perhaps because her father "had such a great mind, he was able to mask it a lot better than some [others]."

After retiring from the NFL in 1973, Farr owned about a dozen car dealerships in several states. He starred in memorable TV commercials wearing a red cape, like Superman, pretending to fly around fighting high car prices. His persona was "Mel Farr Superstar."

With revenue topping $568.4 million, according to a 2002 report by Automotive News, at one point, Farr had the largest black-owned company in the country.

"He was an amazing man with a larger-than-life personality," said his wife, Jasmine Farr, whom he married in 2013. "He was a great athlete, a great businessman, a great family man and a great person. One of a kind. He would light up a room with his presence."

Bartell told Outside The Lines she is thankful Farr's symptoms weren't worse.

"We didn't have to see his health deteriorate to a point where the Mel Farr that everyone knew and loved was unrecognizable," she said.

"Football allowed us to live out the American dream, and it's so crazy that the game that we love so much can also contribute to the death of my dad," she added. "That's a tough pill to swallow."

Now his widow is working to keep his legacy alive recently starting the "Mel Farr Superstar Scholars program" at a Cornerstone charter school in Detroit.

Four months after he died, Jasmine Farr gave birth two weeks early to a baby girl named Melia who was born on Farr's birthday, November 3. Melia is now 1.

"It's divine intervention. She is a blessing and a gift from him," Jasmine Farr said. "We will now celebrate both of them on that day."