Police questioned three people but no arrests have been made in the Sunday evening death that happened as the Kansas City Chiefs played the Denver Broncos inside the stadium, said Kansas City police spokesman Darin Snapp. The cause of death was not immediately made public. Snapp said the man was in his 20s, but did not release his name.

“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.”

The owner of the car returned with his son and found the man who “did not belong” inside the vehicle, Snapp said. The two men scuffled, the man collapsed and the son ran for help, he said. When the paramedics arrived, the man was unconscious on the ground. The paramedics administered first aid and the man was taken to a hospital where he was declared dead, Snapp said.

It was not clear if the men knew each other, nor if the owner of the car had been watching the football inside the stadium or was tailgating with other fans in the parking lot as the game took place.

Chiefs spokesman Ted Crews said the team was aware of the incident but could not comment further because of the police investigation.

Police were talking to several witnesses, and three people were taken to the Kansas City Police Department’s headquarters to be questioned. Snapp said they are not considered suspects in the death.

“Right now they’re persons of interest,” he said.

The death came one year to the day after Chiefs linebacker Jovan Belcher shot and killed his girlfriend, Kasandra Perkins, on Dec. 1, 2012, at a home not far from the stadium. Belcher then drove to the team’s practice facility and fatally shot himself 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.