A beggar who regularly held the door open for change at a Hell’s Kitchen 7-Eleven was fatally shot in the neck inside the store Thursday morning by a rival panhandler now on the loose, police said.

Shoppers were perusing the aisles inside the corner chain convenience store at Eighth Ave. and W. 39th St. when a fight over turf broke out inside between the victim and his killer at about 10:30 a.m., cops and witnesses said.

Workers in stores adjacent to the 7-Eleven said that arguments and fights were common at and around the convenience store — particularly among a few local homeless men who brawl over who would open the doors for customers.

“You see the arguments, the fights out here all the time,” the superintendent of a commercial building near the store told The News. “There’s always something going on here, all hours of the day and night.”

Cops found the victim, believed to be in his 40s, shot in the neck and dead at the scene. Cops are working to determine his identity.

A porter in the commercial building next door said the 7-Eleven is a “magnet for trouble.”

“Everybody tends to fight over the door,” he said. “That door is like territorial”

“I opened the door and stepped in, and inside of two seconds I heard an argument,” said one shopper who wished not to be named. “I heard ‘P—y! P—y!’ and then a bang, and I turned on my heels and walked out.”

“All these people came filing out after me,” the shopper added.

A friend of the victim, whom he knew by the nickname “Beezy,” said the victim often held the door to the 7-Eleven open for change while providing “unofficial security.”

“That’s my man,” said the 22-year-old pal, who would only identify himself as Huby G. “[He’s a] cool dude. Calm, cool, and collected. I don’t know what altercated this right here, but, yeah, it’s crazy out here.”

Besides holding the door open, Beezy would “hold the store down,” Huby G said.

“He’s a security guard. [He’d] stop with the thieves,” he said.

The gunman, who was wearing a mask, green puffer coat, dark pants and a black backpack, ran out of the store and was last seen heading downtown on Eighth Ave. He has not been caught.