It started around 6:20 p.m. on Monday at Sierra and Clark.
Police say a man was involved in a brawl with one or two others inside the park.
The 20-year old man was taken to Community Regional Medical Center where he later died.
Another man who was involved in the fight was also taken to the hospital for his injuries.
Police first believed the death was related to the fight, which would be classified as a homicide investigation.
But now they believe it may have been a medical emergency or that the victim had some sort of accident that led to his death.
At this time, no one is under arrest pending the results of an autopsy.