(CBS) Friends of Rashaan Salaam saw early signs of chronic traumatic encephalopathy in him before he died and fear the physical and mental toll that football took on Salaam contributed to a death that’s being investigated as a suicide, the New York Times reported this week.

The 1994 Heisman Trophy winner and former Bears running back, Salaam had mood swings, and many friends believe he suffered from depression, they told the Times. Salaam’s family didn’t comment for the article, in which Salaam was characterized as a “recluse” who spent most of his time alone in his condo in the Denver suburbs and only went out occasionally, and usually by himself.

The former Bears running back and Heisman Trophy winner, Salaam was found dead at 42 in a park in Boulder, Colo. on Dec. 5. Officials believe he committed suicide, as a gun was found nearby him and there weren’t signs of foul play.

Salaam won the Heisman Trophy in 1994 while at Colorado. He was the Bears’ first-round draft pick in 1995, but his NFL career lasted just three seasons and was marked by injury problems. Former Colorado teammate T.J. Cunningham and others felt that always wore on Salaam.

“Rashaan was 20 years old when he won the Heisman Trophy,” Cunningham told the Times. “To achieve the epitome of success at 20, but then you can’t get to that point again — what did that do to Rashaan?”

Cunningham also spoke to the belief that Salaam had CTE and contributed to his death.

“C.T.E.? He showed all the symptoms,” Cunningham said, “and C.T.E. probably added to that.”

Others further explained.

“He felt people viewed him as a failure,” said David Plati, an associated athletic director at Colorado who was a friend of Salaam’s.

Read the full story here.

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