The family of Vincent Jackson, the retired three-time Pro Bowl N.F.L. wide receiver who was found dead in a Florida hotel room on Monday, donated his brain to researchers at Boston University to determine if he had chromic traumatic encephalopathy, or C.T.E., the degenerative brain disease linked to repeated head trauma.

“Vincent being who he was would have wanted to help as many people as possible,” said Allison Gorrell, a spokeswoman for the Jackson family, in a phone interview Wednesday. “It’s something his family wanted to do to get answers to some of their questions.”

Many unanswered questions, including his cause of death, remain about Jackson’s demise. While it could take weeks to finish an autopsy, Hillsborough County Sheriff Chad Chronister said in a radio interview on Wednesday that Jackson, 38, had health problems associated with alcoholism, which Chronister said were cited in the unreleased autopsy report. He also said the Jackson family told him that they believed that concussions may have been a factor in his behavior.

Gorrell said the sheriff did not speak for the family. C.T.E. can only be diagnosed posthumously and researchers at Boston University, which houses the world’s largest brain bank devoted to cases involving the disease, said that determination can take months. The severity of a player’s C.T.E. is related to the number of years that he played football and the number of hits he endured, researchers have found.

The brain bank has received a growing number of donations harvested from players who were 34 years old or younger at the time of death. More than half of those athletes had C.T.E.

A married father of four, Jackson was widely admired in and out of the N.F.L. for his community service and business acumen. A 12-year N.F.L. veteran who played with the San Diego Chargers and the Tampa Bay Buccaneers, Jackson was voted Tampa Bay’s nominee for the Walter Payton Man of the Year Award, which recognizes community service, four years running during his five seasons there. He was a union representative in the N.F.L. Players Association and one of the named plaintiffs when the union sued the league’s owners during the 2011 lockout.

After retiring from the N.F.L. in 2018 at 35, he continued to help military families through the Jackson in Action 83 Foundation. He had not played since the 2016 season. Jackson’s father served in the United States Army and Jackson and his wife, Lindsey, wrote a series of children’s books about growing up in military families. He won the Distinguished Community Advocate Award in 2018 from the Tampa Bay Sports Commission.

He had been cited for his smooth transition from the N.F.L. into real estate development.

According to the Hillsborough County Sheriff’s Office, Jackson was found at the Homewood Suites in Brandon, Fla., just a few miles east of Tampa, where hotel staff said he had been staying since Jan. 11. Jackson’s family reported that Jackson was missing on Feb. 10. Two days later, sheriffs found him at the hotel and “after assessing Jackson’s well-being,” canceled the missing persons case.

A housekeeper found Jackson dead on Monday morning.

Jackson was a straight-A student in high school and majored in business at Northern Colorado University, where he graduated as the school’s career leading receiver. He was also a starter on the Bears’ basketball team for two seasons, leading the team in scoring both years.

The Chargers drafted Jackson in the second round in 2005, and after an injury-filled rookie year, he quickly became a mainstay of the team’s pass-first offense. He was named to the Pro Bowl in 2009, 2011, and again in 2012, his first season with the Buccaneers. He still holds the Buccaneers’ record for most receiving yards in a game, 216.

During his N.F.L. career, he caught 57 touchdowns and had six seasons with more than 1,000 receiving yards.

According to NFL.com, Jackson was arrested twice, in 2006 and again in 2009, for driving under the influence. After the second arrest, he was sentenced to four days in jail and five years of probation and was suspended by the league for three games.

James Lofton, the Hall of Fame wide receiver, coached Jackson in San Diego and remembered Jackson as exceptionally bright and motivated. He recalled, too, when Jackson called him at 4:15 a.m. to apologize for his 2006 arrest.

“We are part of society, and the same ills that get people in society get us, too,” Lofton said of N.F.L. players. “He just didn’t seem like the person who would have met a tragic death.”

Greg Camarillo, a former N.F.L. receiver, was roommates with Jackson at the Chargers’ training camp in 2005 and now has a student support role in the University of San Diego athletics department. Camarillo said he was shaken by Jackson’s death and posted to Twitter several messages Monday about professional football players’ struggles in retirement.

Many players, Camarillo said, have difficulty coping after they leave the N.F.L. because lose their identity and find it difficult to forge a new path without it.

“It could happen to me or any former player,” Camarillo said in a phone interview Thursday. “Vince is not drastically different than anyone else, including me.”

Gillian R. Brassil contributed reporting.