Authorities said that Thomas was found dead in his home and his death might have been caused by a previous medical issue.
LaTonya Bonseigneur, a first cousin who was extremely close with Thomas, believes that 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 on Friday morning. "We're not sure when he died. We just spoke with him yesterday."
Former teammates also said that Thomas might have been suffering from seizures over the last few months.
On Friday, the Broncos released a statement on Twitter 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."
"Demaryius' humility, warmth, kindness, and infectious smile will always be remembered by those who knew him and loved him,” the statement continued.
Thomas’s alma mater Georgia Tech and head coach Geoff Collins paid tribute to him in a statement calling him by his nickname "Bay Bay."
"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," Collins said. "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."
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."
Born in Montrose, Georgia, Thomas was a three-sport star in basketball, football, and track at West Laurens High School in Dexter, Georgia.
After high school, Thomas went on to excel at Georgia Tech breaking many school and Atlantic Coast Conference (ACC) records. In the 2010 NFL draft, he was selected by the Denver Broncos in the first round with the 22nd pick. He was the first wide receiver chosen in the draft.
Throughout his stellar career, Thomas, who would have turned 34 on Christmas, was named to five straight Pro Bowl teams and was a part of the Broncos squad that won Super Bowl 50. In addition to the Broncos, he played for the Houston Texans and ended his career with New York Jets.
We extend our prayers and condolences to the family and friends of Demaryius Thomas