He was a trustee on the player benefits board for the NFL Players Association, a member of the PUSH Excel board of directors and held a seat on the Bears alumni advisory board.

Duerson also had contacted former agent Steve Zucker in January to put out feelers for NFL coaching opportunities. Duerson's Bears teammate Leslie Frazier, now head coach of the Vikings, told reporters Duerson had left him a message a couple of weeks ago about coaching. To Frazier's regret, they never connected.

"Dave had a lot of irons in the fire," said DaRayl Davis, a business associate who had been in contact with Duerson recently. Davis and Duerson were planning a March meeting of NFL alumni to address collective bargaining issues for retirees and potential investors.

Though Duerson had told teammates at a November reunion of the '85 Bears that he was thinking about a move back to Chicago, where he remained an iconic figure, he appeared comfortable in Sunny Isles Beach.

Duerson and his wife had purchased the condo as a second home. Duerson moved there after their split.

Wednesday, Feb. 16: Duerson speaks with his ex-wife on the phone for the last time. They talk about Taylor's upcoming volleyball tournament and which games her father would attend.

Some trace Duerson's downward spiral to Feb. 3, 2005. That's when Notre Dame campus police reportedly observed Duerson throw his wife against a wall at the Morris Inn on the edge of campus. He was charged with misdemeanor battery, and the incident cost Duerson his seat on Notre Dame's board of trustees.

In an interview in November with Rob Trucks, an author researching a project on Americans turning 50, Duerson called the incident "my biggest regret." According to Trucks, Duerson said: "My wife and I had an argument in South Bend, and, you know, I lost control for three seconds. That was a one-time event. The most disappointing of my entire life, but one that will never, ever be repeated."

Dave Duerson filed for divorce in Lake County on May 2, 2007. Alicia Duerson filed for divorce on July 8, 2008. The divorce was granted on Sept. 21, 2008.

The Duersons were awarded joint custody of Taylor, who was to live with her mother but see her father up to one weekend a month and several weeks in the summer. He was ordered to pay $1,406 in monthly child support and insurance premiums.

Thursday, Feb. 17, 3 a.m. EST: Alicia Duerson receives a text message from her ex-husband. "I love you. I always loved you. I love our kids," he wrote. He follows with another text, asking that his brain be donated to the NFL. She calls him several times. No answer. Then, a final text: "Please, see that my brain is given to the N.F.L.'s brain bank."

What would the NFL want with Dave Duerson's brain?

About three years ago — more than a decade removed from an 11-year career that took him from the Bears to the Giants to the Cardinals — Duerson noticed something was not right.

It started mildly. Progressively, it became more problematic. Blurred vision. Headaches. Memory loss. Problems spelling common words. He talked specifically of pain on the left side of his brain.

When he was in Chicago not long ago, the former hard-hitting safety couldn't remember how to get places. "That aggravated him because he could always go anywhere in the city or state without having to look at a map," Alicia Duerson said.

He couldn't remember when and where Taylor's volleyball tournament was. His ex-wife had to remind him, repeatedly.

Duerson was aware of his problem. He began writing everything down. He took to making detailed notes of conversations, showing little trust in his memory.

"If you knew Dave, he was a brilliant man," Alicia Duerson said.

Duerson had a bachelor's in economics from Notre Dame and a certificate from the Harvard Business School's Executive Education Program. "He had no problems formulating words, or keeping a thought pattern," Alicia Duerson said. "But lately he felt he wasn't the same person. He was unable to do some simple things."

Friends and family members feared Duerson suffered from chronic traumatic encephalopathy, or CTE, the brain disease that has been found in at least a dozen retired football players. He appeared symptomatic, they said. But only a posthumous study of his brain tissue can confirm the presence of CTE.