Mount Airy's picturesque Germantown Avenue, a cobblestoned Main Street filled with mom-and-pop businesses and family-friendly restaurants, was decorated Friday morning with something unusual: leftover chalk outlines of shell casings.

It was the result of a quadruple shooting outside a nightclub after 2 a.m. Friday, the first time that residents and proprietors on the vibrant main drag could recall such an eruption of violence in the Northwest community known for its diversity.

"There really has never been any kind of incident like that," said Sherri Hall, owner of Blacqskirt, a boutique on Germantown Avenue.

Mario Zergani, whose family's Golden Crust Pizza shop has been on the avenue for years, said simply, "This is Mount Airy. People don't do something like that."

Around 2:15, a fight broke out inside 7165 Restaurant, formerly North by Northwest, said Lt. Dan Brooks of Northwest Detectives. About two dozen people were inside for what police described as an open mic night.

Thomas Hoover, 29, who lives on the block and said he is a regular at the bar, said he believed Thursday night was scheduled to be a "twerking contest." Hoover was home when the shooting happened, and said he heard the "pop-pop-pop" of shots outside his window and looked out in disbelief.

"I thought that [stuff] happened in North" Philadelphia, he said.

The bullets began flying after the bar's management ordered the fighting patrons to leave, according to Brooks. As the scuffle continued outside, the suspected shooter went to his car, retrieved a gun, and began firing. Police said the man, whom they did not identify, unloaded about six or seven shots.

Three men and a woman were hit, Brooks said. The woman, 26, worked at the bar and was struck in a knee. Police did not identify her or the other victims, but said the men were all either 25 or 26. One of the men was hit in the back and a leg, another in a hand, and the third in a leg and the right side, police said.

Each was hospitalized and reported in stable condition, according to police.

A driver trying to take one of the victims to a hospital crashed a car a few blocks from the scene, Brooks said.

The shooter had not been arrested by Friday night, but police said the suspect was a black man in his late 20s or early 30s with dreadlocks who fled in a red or maroon car.

Brooks said police were interviewing victims and witnesses and reviewing surveillance footage from the area. Anyone with information can contact Northwest Detectives at 215-686-3353.

A bullet hole remained Friday morning in a glass window pane at the restaurant, along with chalk circles dotting the sidewalk along Germantown Avenue. Attempts to reach the bar's owners or employees Friday were unsuccessful.

The restaurant remained closed Friday night. The damaged window was covered with plywood. Nearby businesses were open as usual.

Police statistics show Mount Airy is one of the least violent neighborhoods in the city, with just four violent crimes recorded in the last month.

Farah Jimenez, a longtime Mount Airy resident and a member of the School Reform Commission, said the shooting should be looked at as an exception rather than the rule.

"It doesn't reflect in any way, I think, the safety and the future of the neighborhood," Jimenez said.