When a 53-year-old man died Sunday after attending the New England Patriots game, videos and witness accounts quickly surfaced online detailing a fight that resulted in the fan being punched in the head.

But prosecutors are now saying that preliminary autopsy results indicate that Dale Mooney's death does not appear to be the result of a traumatic injury suffered during the scuffle, videos of which authorities reviewed during an investigation. Rather, the Newmarket, New Hampshire man experienced an unspecified "medical issue" that led him to die after he was rushed to a nearby hospital, the Norfolk District Attorney's Office said Wednesday in a media release.

"Our investigation has included numerous law enforcement interviews and the examination of multiple angles of video capturing the scuffle prior to Mr. Dale Mooney’s collapse," the district attorney's office said in a statement. "Our investigation remains open and ongoing."

The district attorney's office did not immediately respond to USA TODAY's request to specify the nature of Mooney's medical emergency.

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What happened to Patriots fan Dale Mooney?

Mooney, an apparent lifelong Patriots fan, had been attending Sunday night's home game against the Miami Dolphins at Gillette Stadium in Foxborough, Massachusetts.

During the fourth quarter of the Patriots' eventual loss, police and firefighters were called around 11 p.m. to the 300-tier section of the stadium to give medical attention to Mooney after what witnesses have said online was an altercation in the stands.

Mooney was rushed to Sturdy Memorial Hospital in Attleboro, where he was pronounced dead just before midnight, the district attorney's office has said.

Lisa Mooney, Dale Mooney's wife, was quoted in multiple news reports as saying that her husband had been a Patriots season-ticket holder for 30 years.

USA TODAY has left a message Wednesday morning with the Patriots seeking comment on the incident.

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Witness describes fight caught on camera

Footage shared online shows Mooney wearing a Patriots jersey and engaging in a confrontation that turns violent. An assailant who cannot be clearly seen lands a blow on Mooney's temple, sending him crumpling into his seat unconscious.

Joey Kilmartin of Nashua, New Hampshire, was a spectator at Sunday’s game who claims to have witnessed the confrontation. Kilmartin told local news outlet MassLive.com that back-and-forth verbal jabs between Patriots and Dolphins fans throughout the game preceded the physical altercation near the end of the fourth quarter.

“The Dolphins fan walks over and clearly punches him in the face,” Kilmartin told MassLive, adding that he provided his account to police. “[He] gets knocked out and you can tell right away he’s not OK.”

Kilmartin did not immediately respond to a message left Wednesday morning by USA TODAY.

No charges have been filed in relation to Mooney's death as of Wednesday. The Norfolk District Attorney's Office is asking that anyone with information call the Massachusetts State Police detective unit assigned to its office at 781-830-4990.

Eric Lagatta covers breaking and trending news for USA TODAY. Reach him at [email protected]