9:15 AM PT -- Police tell TMZ Sports ... Payne was shot and killed early Monday morning in Florida.
According to the Orange County Sheriff's Office, officers responded to a report of a shooting at around 1:37 AM and discovered Payne suffering from a gunshot wound.
Cops say Payne was transported to a hospital, but later died there.
A spokesperson for the sheriff's office says 29-year-old Lawrence Dority was identified as the shooter ... and was ultimately arrested on a warrant for first-degree murder.
Former Michigan State men's basketball star Adreian Payne has died ... his former teammate announced on Monday. He was just 31 years old.
Details surrounding the death have not yet been revealed ... but Jared Sullinger -- the former Ohio State Buckeyes star who played with Payne at some point in their basketball careers -- announced the sad news via his Twitter page.
"Hate the news i received this morning…." Sullinger said in a tweet. "Rest Easy to my brother/Teammate @Adreian_Payne."
Payne became a massive star for the Spartans after arriving on the East Lansing campus in 2010 ... recording 16.4 points per game and 7.3 rebounds in his senior season in 2013. That year, Payne helped lead MSU to an Elite Eight appearance.
Adreian went on to be taken by the Atlanta Hawks with the #15 overall pick in the 2014 NBA Draft. He bounced around the Association for several years after that, before eventually moving overseas to play professionally.
Payne last played for Juventus Utena in Lithuania in the 2021-22 season.
Off the basketball court, Payne was perhaps best known for his relationship with 8-year-old cancer patient Lacey Holsworth. Adreian befriended her while at MSU, and the two grew so close, they referred to each other as brother and sister.
In fact, Holsworth -- who later passed away in 2014 -- joined Payne on his senior night at Michigan State.
Famed college basketball head coach Archie Miller mourned Payne's death on Twitter on Monday ... writing, "Sad to hear the passing of Adreian Payne this morning."
"Started watching him while he was in 10th grade, remember his grandmother on his visit. Loved seeing him develop at Michigan St. and become an NBA player. [Prayers] for his loved ones, Spartans, and Dayton, OH. #RipAP"