Five years after hanging up his cleats, former Kansas City Chiefs offensive tackle Jim Tyrer was picked as a first-ballot finalist for the Pro Football Hall of Fame in 1980, a more than justified nomination given the legendary career he enjoyed.

At the time none could dispute Tyrer – a Super Bowl champion, six-time All-Pro and three-time AFL winner – being duly rewarded for his success on the field after 13 seasons with the Chiefs and one closing chapter in Washington.

Yet the harrowing and tragic events which occurred shortly after left a disturbing asterisk on his legacy forever.

In the early hours of September 15, Tyrer shot and killed his wife Martha before turning the gun on himself in a murder-suicide which sent shockwaves rippling through America.

The 41-year-old inevitably failed to make it into the Hall of Fame that year and, as the mystery over what caused his devastating actions has been dissected by many, it has stayed that way in the 44 which have followed.

However, in an astonishingly late U-turn, that could change next year after Tyrer was controversially named on the ballot as a 2025 finalist.

Nominated in the Seniors category for players whose careers ended before 1999, Jim could finally break into the Hall almost half a century since his infamous murder-suicide.

His nomination has of course sparked major contention; with a large majority left bewildered that a man who murdered his wife could potentially receive such a prestigious honor, but others are adamant that he deserves to be included on football achievements alone, while insisting that his fatal outburst on September 15, 1980 was a heartbreaking effect of chronic traumatic encephalopathy (CTE).

Tyrer had been dealing with depression and severe headaches that experts now believe may well have been CTE – the degenerative brain disease that has been found in many former NFL players who endured repeated blows to their heads in their career.

According to Boston University CTE Center, the disease is associated with ‘memory loss, confusion, impaired judgment, impulse control problems, aggression, depression, suicidality, parkinsonism, and eventually progressive dementia.’

Not many players were renowned for using their heads to block more than the Chiefs icon, and doctors are convinced that he had CTE at the time of the murder-suicide.

Tyrer’s son, Brad, has also spoken of his belief that his dad was suffering from the disease in recent years.

The day before the murder-suicide, Jim had spent the afternoon watching Kansas City take on the Seattle Seahawks at Arrowhead Stadium with his other son Jason.

And as the Seahawks got the better of his former team in a 17-16 victory, fans sitting near Jim and Jason later recalled the ex-defender being ‘oddly transfixed by the action’, according to Slate.

It is believed he spent most of the game ‘staring at the field, paradoxically preoccupied yet distant’ while watching the Chiefs come unstuck, which becomes a more chilling memory when taking into account what played out the following day.

As well as potentially battling with CTE, Tyrer is also believed to have been struggling with financial difficulties in the months leading up to the murder-suicide.

After turning down a $25,000 offer from the Chiefs to work for them as a scout, the 1970 First Team All-Pro’s post-football investments reportedly amounted to three failed businesses and debts ranging between $100,000 and $250,000.

Fred Arbanas, Jim’s best friend, felt his close pal had been depressed for five days before the murder-suicide, a Washington Post story from September 20, 1980 reads.

‘He had just left a job interview and said that, at age 41, he now was competing for work against recent college graduates, men only slightly older than his daughter,’ the article said.

Though regardless of the tell-tale signs of depression he had been emitting, Tyrer’s impulsive act of violence came as a significant shock to those closest to him.

The 6ft 6in and 280lbs ex-football player was considered somewhat of a gentle giant off the field, while his close friends rarely saw him drunk.

‘Jim Tyrer was the unlikeliest suicide-murderer to those who knew him,’ Michael Oriard, one of Tyrer’s teammates, wrote about him in 1982.

No test for CTE existed in the early 1980s, meaning the murder-suicide proved much more of a mystery in the first few years after that tragic night on September 15.

Now experts are convinced the degenerative brain disease is the most plausible explanation for Tyrer’s murderous actions.

‘If it walks like a duck, it quacks, it has webbed feet and water goes off its back, it’s not a zebra: It’s CTE,’ Doug Paone, the doctor who treated Tyrer just days before the night in question, told the Kansas City Star last week. ‘(Tyrer) would be the poster child for CTE.

‘I’m sure that if he never had played offensive line, or had never been a football player, for that matter, he would never have killed his wife and himself.’