A co-owner of a Bronx watering hole was shot and critically wounded early Friday after he refused to serve alcohol to a drunken assailant, police said.

Mario Ramirez, a 52-year-old father of three, got into a heated argument with the unidentified suspect inside the El Rey de Copas Restaurant Bar on White Plains Road in the Allerton section around 1 a.m., cops said.

The suspect, who’s in his 40s, whipped out a gun and pumped two bullets into Ramirez’s neck and torso before fleeing with the weapon, cops said.

Ramirez was brought to Jacobi Hospital, where he was listed in critical but stable condition.

His brother, Gustavo Ramirez, 49, told The Post that he rushed to the hospital after doctors called him to deliver the bad news.

“[Mario] is doing better. He’s in intensive care. But he is still in danger. Now he is out of the operation, but he is sleeping,” Gustavo said.

Gustavo said the violence erupted after the drunken gunman staggered into the bar and demanded a beer.

“The waitress said he looked intoxicated. My brother said, ‘We don’t serve anyone who appears intoxicated.’ He [the perp] asked again. The waitress said no and he asked for the manager,” Gustavo said.

“My brother explained to him why he couldn’t be served and he stood up and shot my brother in the chest,” Gustavo added.

After Mario collapsed, the perpetrator stood over him and shot him in the neck, Gustavo said.

The gunman then “walked down the street, wobbling and staggering,” said Gustavo.

Approximately 15 patrons were in the bar at the time of the shooting and “they all ran, scattered,” when the shots rang out, Gustavo said.