ENGLEWOOD, Colo. -- Former Denver Broncos wide receiver Demaryius Thomas, whose quiet demeanor belied a burning desire to achieve what he routinely called "everyday greatness," has died at age 33, according to police.

Roswell, Georgia, police said Thursday night that Thomas was found dead in his home. Preliminary reports, according to police, indicated Thomas' death might have resulted from a medical issue.

LaTonya Bonseigneur, a first cousin who grew up with Thomas, so close they considered themselves siblings, told The Associated Press that the family believes he died from a seizure.

"He had been suffering from seizures for over a year, and we believe he had a seizure when he was showering," Bonseigneur said early Friday. "We're not sure when he died. We just spoke with him yesterday."

Former teammates also noted Thursday night that Thomas might have been having seizures in recent months.

The Broncos released a statement early Friday, mourning the loss of "an incredible player and a special person."

"We are devastated and completely heartbroken by the sudden, tragic passing of Demaryius Thomas," the Broncos said. "D.T. was beloved by our entire organization, his teammates and coaches, and our fans. Recently retiring as a Bronco, we were very much looking forward to celebrating Demaryius for years to come as one of the greatest players in franchise history."

The Broncos went on to add, "Demaryius' humility, warmth, kindness and infectious smile will always be remembered by those who knew him and loved him."

We are devastated and completely heartbroken.

Demaryius' humility, warmth, kindness and infectious smile will always be remembered by those who knew him and loved him. pic.twitter.com/0GLZIr6UP3

— Denver Broncos () December 10, 2021

Thomas, who would have turned 34 on Christmas, had announced his retirement from the NFL in June with a short video with a peace sign and his characteristic smile.

"I'm Demaryius Thomas. I finally came to a decision to hang it up. ... I'm going to retire and I'm going to retire a Denver Bronco," he said. "... I'm done and I did well."

Hall of Fame quarterback Peyton Manning, who played with Thomas for four seasons, also released a statement early Friday.

"DT was a better person than he was a player, and he was a Hall of Fame player," Manning said. "That tells you how good of a person he was. He treated my kids like they were his own. He was there for every teammate's charity event. ... Absolutely devastated."

Several other former teammates and opponents took to social media early Thursday night as reports of Thomas' death began to appear.

Broncos wide receivers coach Zach Azzanni, who coached Thomas in his final season with the Broncos in 2018, tweeted: "I'm so sad ... I'm heartbroken. I'm at a total loss. I'm sick ... I'm crying I'm just ... I don't know. The Azzanni family will always love you DT. I'm blessed to have known you. RIP #88."

Georgia Tech, where Thomas played college football, posted a picture with the caption "Rest in peace, Bay Bay" -- referring to Thomas' nickname.

"I know I speak on behalf of the entire Georgia Tech football family when I say that we are heartbroken by the news of Demaryius's passing," Georgia Tech coach Geoff Collins said in a statement. "I first got to know Bay Bay during his recruiting process and was fortunate to be a member of the Tech football staff during his true freshman season in 2006. We have grown increasingly closer through the years. I will always remember what a thrill it was for our players when he was able to stop by and spend some time with us during fall camp this past August. Bay Bay was truly one of my favorite people. I will miss him terribly."

DeMarcus Ware, a teammate of Thomas' for three seasons, posted a photo of Thomas and himself Thursday night captioned simply "heartbroken." Broncos defensive end Shelby Harris posted "so sad man," and former Thomas teammate and linebacker Brandon Marshall posted "Love forever bro."

They spoke for many as hundreds of Broncos fans posted videos and other tributes.

Thomas had been honored by the Broncos during their home opener Sept. 26 against the New York Jets.

He was the first of two first-round picks for the Broncos in the 2010 NFL draft -- Tim Tebow was the other -- and spent nine seasons with the team. He finished his career as the Broncos' second-leading receiver (9,055 yards), behind only Rod Smith. He is third in franchise history in catches (655) behind Smith and Hall of Famer Shannon Sharpe.

Woke up and saw the really devastating news about my teammate and friend, Demaryius Thomas. So many are going to remember him for his athletic ability... but I'll be remembering him for his kindness, his smile that would light up a room, and the love he had for those in his life. pic.twitter.com/gNVzmJ503X

— Tim Tebow () December 10, 2021

Thomas played in 10 seasons overall with the Broncos, Houston Texans and Jets and finished with 724 catches for 9,763 yards and 63 touchdowns.

"D.T. was the complete package as a wide receiver, growing into one of the very best at his position," Broncos president of football operations John Elway said in June after Thomas retired. "The combination of his size, speed, strength and athleticism was unmatched. Demaryius' remarkable consistency and production were instrumental in our offense setting historic records and our team winning a lot of games, including two AFC Championships and Super Bowl 50."

The Jets honored Thomas in a tweet, saying "A brilliant career on the field with a light that always shone brighter off of it. Gone way too soon. But your impact remains." The Texans also expressed their condolences in a tweet.

Thomas had a foot injury -- he had been injured working out before the 2010 draft -- in his first two seasons in the NFL but flourished when healthy. With the arrival of Manning in 2012, Thomas had at least 90 receptions and 1,300 yards in four consecutive seasons, joining Hall of Famers Marvin Harrison and Jerry Rice and Rams legend Torry Holt as the only players to reach those totals over four consecutive seasons.

In the Broncos' record-setting season in 2013 -- Manning set NFL records for passing yards (5,477) and touchdowns (55) as the Broncos scored a league-record 606 points -- Thomas finished with a career-best 14 touchdowns. The following season, he finished with a career-best 1,619 receiving yards.

Thomas routinely said Manning revealed parts of the game that enabled him to elevate his play. Manning had called Thomas one of the best receivers he had played with in his career. When Manning's children would come to practices, Thomas was routinely the first player they would run to as the players had become close friends. Thomas caught Manning's 509th career touchdown pass, which gave the quarterback the career record at the time. A picture of Manning and Thomas posing with a handwritten sign after the game has been on display at the Pro Football Hall of Fame.

For many among the team's faithful, Thomas' signature play is the catch-and-run 80-yard touchdown, on a short pass from Tebow, in the first play of overtime to give the Broncos a victory over the Pittsburgh Steelers in the AFC wild-card game following the 2011 season.

"For as humble and soft-spoken as Demaryius was during his nine years with our organization, you would have never known he was such a dominant player in our league," Broncos CEO Joe Ellis said in a statement in June. "D.T. was an integral part of one of the greatest offenses of all time, putting up record-setting numbers and giving Broncos fans so many unforgettable memories. I've never heard Empower Field at Mile High louder than his game-winning touchdown in overtime against the Steelers in the playoffs."

Thomas' teammates, coaches and friends have often referred to all he had overcome to reach Georgia Tech and the NFL. His mother, Katina Smith, went to prison on drug charges when Thomas was 11 years old. With his father in the military, Thomas began working before school, picking corn, peas and butter beans for farmers to help support himself.

His mother's sentence was commuted by President Barack Obama in 2015, and Smith saw her son play football in person for the first time in the Broncos' playoff win over the Steelers in January 2016.

Manning, who kneeled down on the game's final play, gave Thomas the football from that play to give to Thomas' mother.