The death of a man during Sunday night's New England Patriots game against the Miami Dolphins is being investigated by Massachusetts State Police and a county district attorney's office, according to multiple reports.

The 53-year-old was identified as Dale Mooney by the Norfolk District Attorney's Office, a report from NBC News said.

He was in 300-level seating inside Gillette Stadium in Foxborough, Mass., when he had an "apparent medical event" before 11 p.m., state police reportedly said. Police and firefighters responded and he was pronounced dead at Sturdy Memorial Hospital, according to the report.

The Norfolk District Attorney’s Office is investigating the death as part of "normal protocol," the prosecutor's office said, via NBC News.

Charges have yet to be filed in connection to Mooney's death. Progress of the active investigation will depend on an autopsy, which could be conducted Tuesday, the District Attorney’s Office's statement reportedly said.

Police are "investigating the facts and circumstances of the man's death, including the sequence of events prior to the medical incident," David Procopio, a spokesman for the state police, told The Foxboro Reporter.

Witnesses described a fight breaking out before Mooney's death to NBC10 Boston:

"It was really one punch that I saw and the victim got punched really hard on the side of the head, and went down. He's a bigger guy but he just crumbled," one witness told the local outlet.

The witness went on to describe a "brutal" scene that unfolded as first responders arrived and performed compressions on Mooney for 10 minutes:

"It was pretty heartbreaking and the game was still going on so the general public clearly knew what was going on in our section so the game was going on, people are cheering for the Patriots comeback, and this poor guy has passed away before our eyes," the witness said.

There are multiple cell phone videos circulating of the incident. One shows security attempting to break up the fight.

Lisa Mooney told Boston's ABC6 that her husband, Dale, was being provoked by other fans during the game, which led to a fight where another man allegedly punched him in the head three times. She added that she wasn't aware of Mooney having a preexisting medical condition.

"It takes a lot to get him mad," Mooney's wife said. "He has the patience of a saint. I don't know what happened."

Mooney's wife told NBC10 Boston that he went to Gillette Stadium to support the Patriots for many years. They were together for more than three decades and had two sons together.