Kansas City police are treating the death of a fan at Sunday’s Chiefs-Broncos football game outside Arrowhead Stadium as a homicide and have three people in custody.

Kansas City Police Chief Darryl Forte tweeted Sunday that authorities were interviewing “multiple parties” about the death of the man, whose name was not released but was identified as being white and in his 20s. The man was lying unconscious in the parking lot and died “after struggling with two subjects,” Forte said. The heated NFL rivalry between the Chiefs and the Denver Broncos did not play a role in the incident, according to the police chief.

Forte wouldn’t name the persons of interest who are in custody. Kansas City television station KCTV said Tuesday that authorities were in Independence, Mo., to carry out a search warrant at a home in connection with the Arrowhead homicide. Kansas City police received a tip that there may be evidence in the home related to the fan’s death.

The homicide occurred in parking lot A of the Truman Sports Complex, which includes Arrowhead Stadium. A fight broke out when the victim got into another person’s car and was spotted by the owner, the Kansas City Star reported. The fight ended with the victim unconscious on the pavement. He died after being taken to a local hospital.

Kansas City Police Officer Darrin Snapp told KCTV that an autopsy is scheduled to determine the victim’s cause of death.

"The main thing we're trying to figure out now is exactly how this person died. The hospital says there's no obvious signs of how he passed away, so we're still waiting on that. We're going to investigate it as a homicide until we find out exactly how the person died," the officer said.

Snapp described the three persons of interest as being cooperative with the police investigation.

"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."

Witnesses described the aftermath of the Arrowhead homicide to the Star.

“They had the caution tape up and they had extra police officers roaming the area, making sure everyone was in control,” Chiefs fan Andy Vaughn told the paper. “At the end of a Chiefs game, there are a lot of really rowdy people and there were a lot of people upset about losing, but it seemed like it was pretty under control.”

Sarah Harrison, a 32-year-old Chiefs fan, said she was in the next parking lot over from where the Arrowhead homicide occurred.

"I walked out after the game mad that we lost, sad, frustrated, and then heard [about the incident]. I don’t even know what to say,” she said.

View the Star's video report on the Arrowhead homicide below: