A 21-year-old man, who was a popular Gaelic football player in Ireland before immigrating to the US, died after a Thanksgiving Day brawl outside a Queens bar – and a fellow Irishman was charged with assault after turned himself in to police Friday, according to reports and sources.

Steve O’Brien, 25, showed up at the 108th Precinct about 8 a.m. and was charged several hours later with assault in connection with the death of Irish native John “Danny” McGee.

“This is a tragedy and our thoughts and prayers go out to the victim’s family, however, Mr. O’Brien is not guilty,” said his defense lawyer Matthew Gartenberg.

McGee and O’Brien were at The Gaslight in Sunnyside to meet mutual friends and allegedly got into an argument outside around 3:45 a.m. Thursday, according to police.

O’Brien fled after cold cocking McGee, who crumpled to the pavement, suffered a cardiac episode and was pronounced dead at Elmhurst Hospital Center, cops said.

It was not immediately clear if the charge would be upgraded after the medical examiner determines the cause of death.

Police questioned a bartender who told them the two men were both highly intoxicated and got into a fight, a high-ranking police source told The Post.

The woman, a friend of both men, provided police with a photo of the suspect from Facebook, according to the source.

McGee, who was originally from Drumlish, a village in County Longford, played Gaelic football and had been a member of the Father Manning Gaels, according to The Irish Sun.

“Everyone in the club is shocked and saddened at the tragic passing of Danny McGee in New York,” the club posted on Twitter.

“Loved by all who knew him he was a star for St. Vincent’s at each age group and played senior with us shortly before emigrating. Our deepest sympathies to his family and friends. RIP.”

Longford County Councillor Martin Mulleady also expressed his condolences to the young man’s family.

“I knew him very well. He was very well got and comes from a highly respected local family,” he told the news outlet. “Danny was a very talented GAA player who played up until under-21 level with Fr Manning Gaels. I coached him myself when he was younger.”

McGee had also played soccer earlier in his life. His former team, Gaels United in Longford, also mourned his death in social media.

“He was a true gentleman, always very friendly with a great smile and sense of humour. He played soccer with great passion and was proud to captain the Longford Kennedy cup team in 2011,” the team said in a statement posted on Facebook.

“We would like to take this oppourtunity to offer our sincere condolences to Dannys parents Colleen & Don, his brother Brian and sister Eva, also to his extended family and friends. May he rest in peace.”

Tributes also poured in from friends, including Rory O’Brien, who wrote on Facebook that he was “proud to call this man one of my best friends.”

“Such an impact he had on so many lives, a person who would walk into a room and put a smile on everyones face an absolute gentleman,” he said.

McGee’s parents planned to travel to New York to take his body back to Ireland, The Sun reported.

A woman living in McGee’s building on 41st Street in Sunnyside said she saw him the night before he died and exchanged pleasantries.

“He’s very nice,” Ana Dziewa said. “We never had an issue. He always said hello. Very clean, very nicely dressed. He worked very hard — two jobs, I think. So I didn’t see him very much.”

McGee lived on the third floor since February, she said, adding that his roommate was away for the holidays.

A spokeswoman for the Irish Department of Foreign Affairs said it is offering consular assistance to the family, according to the BBC.