A man died of injuries he suffered in a fight in the parking lot Sunday at Arrowhead Stadium in Kansas City during the Chiefs’ game against the Denver Broncos.

The fight broke out when the owner of a car in the lot discovered the man, whom police spokesman Darin Snapp said was in his 20s, inside his vehicle and ended with the man lying unconscious on the ground, according to the Kansas City Star, at about 5:20 p.m. CST. Police said three persons of interest were in custody.

“At this time, we’re not calling it a homicide,” Capt. Tye Grant said (via USA Today), “but we’ll investigate it as one.” Police added  in a press release that there were “no obvious signs” of the cause of death.

The fight did not appear to be related to the game or the AFC West rivalry. “They had the caution tape up and they had extra police officers roaming the area, making sure everyone was in control,” Andy Vaughn, a Shawnee, Kan., resident, told the Star. “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.”

The incident occurred exactly one year to the day after Jovan Belcher shot and killed his girlfriend, then drove to Arrowhead and shot himself to death.

The incident is the latest in a string of fan-related incidents at sports events. On Thanksgiving, a Dallas Cowboys fan was beaten by Oakland Raiders fans in Dallas. Last week, a Raiders fan saved a woman who jumped from the upper deck in what reportedly was a suicide attempt at O.co Coliseum in Oakland. Last week, a man fell from a railing at Ralph Wilson Stadium in Buffalo. In September, a man died from a fall outside Candlestick Park at the 49ers-Packers game. In the summer of 2012, a fan died after an escalator fall at Reliant Stadium. Last December, a teenager was seriously injured when he fell from the third deck of the Coliseum. In August, a fan died after a fall at Turner Field.