A person attending Sunday night's Miami Dolphins-New England Patriots game at Gillette Stadium said the man who died after what officials called an "incident" there was punched in the head two times.

In an interview with several local media outlets, Joey Kilmartin said he saw Dale Mooney, a 53-year-old from Newmarket, New Hampshire, confront a rival Dolphins fan whom he had been arguing with during most of the game.

"He [Mooney] went over to Section 311, and he basically engaged in mutual combat with another fan," Kilmartin told The Boston Globe. "A lot of people started trying to pull them apart. ... It looked like somebody was in the middle of them. And then a man in the Dolphins jersey reached over, and he connected with two punches to the victim's head. It wasn't something crazy or out of the ordinary until, 30 seconds later, the guy wasn't getting up."

Kilmartin shot video of what he said happened at the Foxborough, Massachusetts, stadium.

Police and personnel responded to the facility's upper deck shortly before 11 p.m. and found Mooney "in apparent need of medical attention," the Norfolk County district attorney's office said Monday in a news release. Mooney was taken to a hospital, where he was pronounced dead, according to the release.

The results of an autopsy are expected this week, a spokesperson for the district attorney's office said.

Massachusetts State Police are investigating what transpired.

"Numb. I just feel numb. I just can't even believe this is for real," Mooney's wife, Lisa, told Boston's WCVB-TV. "I want to know what happened. What caused this?"

Gillette Stadium officials said in a statement they were "heartbroken" to learn about the death of Mooney, whom they described as a lifelong Patriots fan and a 30-year season-ticket holder.

"We continue to work with local authorities to assist them with their ongoing investigation," the statement indicated. "We extend our sincerest sympathies and heartfelt condolences to Dale's family and to all those who are mourning his loss."

Information from The Associated Press was used in this report.