Authorities say three people have been taken into custody for questioning after a man died in the parking lot of Arrowhead Stadium in Kansas City following the Chiefs' loss to the Denver Broncos on Sunday night.
Kansas City police spokesman Darin Snapp told The Associated Press that the incident was being treated as a homicide but no arrests had been made. Police Chief Darryl Forte added that it did not involve any "fan rivalry."
Police told Fox4KC.com it appeared that a man found a stranger in his car outside of the stadium after the game, and then a struggle ensued. The person found in the car, described as a white man in his mid-20s, collapsed during the struggle.
When paramedics arrived, the man was found lying unconscious on the pavement, Snapp said.
The man was taken to a local hospital where he was pronounced dead. His identity has not been released.
Snapp told The Associated Press the man had his son with him when he returned to his vehicle and that the boy -- whose age was not immediately known -- had run for help when the struggle began.
Snapp said there were no obvious indications of how the man died.
"We don't know if the person had a health condition, had a heart attack. We don't know," Snapp said. "We're going to investigate this as a homicide until we hear differently. Right now it's a suspicious death but we are going to investigate it as a homicide.".
Fans were reportedly unable to leave the parking lot after police closed off the area with crime scene tape, with one saying on Twitter at least 60 cars were stuck behind the tape.
The Chiefs lost to the Denver Broncos, 35-28. Kansas City Chiefs spokesman Ted Crews said the team is aware of the incident but could not comment any further because of the ongoing police investigation.
The death came one year to the day after Chiefs linebacker Jovan Belcher killed his girlfriend, Kasandra Perkins, at a home not far from the stadium. Belcher then drove to the team's practice facility and committed suicide in front of then-coach Romeo Crennel and general manager Scott Pioli.
In September 2012, a gunman attacked a Kansas City Royals employee in the same parking lot, which services Kauffman Stadium as well. The gunman shot the employee once in the abdomen and then returned to his vehicle and committed suicide.
Snapp said police were speaking to several witnesses after Sunday's incident.
"Everyone was very cooperative when we got here," he said. "Everyone that we believed was involved is still here and we're talking to them. Right now they're persons of interest. Like I said, until we find out exactly how this person passed away, we're going to investigate it as a homicide. They're not suspects right now until we find out exactly what happened."
The Associated Press contributed to this report.