MMA Fighter Isaac Johnson Dead at 31 After Fight

MMA Fighter Isaac Johnson has died after being injured during a match near Chicago Friday night.

NBC 5 Chicago reports Johnson collapsed after suffering an injury during his fight against Mario Aleksandrovski at Cicero Stadium.

An ambulance was called to the stadium at 8:38 PM local time to transport “an injured fighter” to the hospital ... and Johnson passed away a few hours later, just after midnight.

The Cook County Medical Examiner's Office has scheduled an autopsy to determine Johnson's cause of death.

Joe Goytia -- promoter of the Matador Fighter Challenge, the event Johnson was taking part in -- told Fox 5 Washington, D.C. that Johnson passed the mandatory physical before the bout.

Mission MMA & Fitness -- a popular gym for MMA fighters in Chicago -- shared a tribute to Isaac ... calling him "an incredible person. A great friend and loving father. He is missed by us all." The gym also asked for people to give his family privacy.

Isaac was 31.