GLENDALE, Ariz. (AP) — A fight between groups of people with a history of “bad blood” escalated Sunday night into a shooting outside a concert and car show at a suburban Phoenix restaurant, leaving three dead including a teenager and five others injured, police said.

The shooting outside El Camaron Gigante Mariscos & Steakhouse was an “isolated incident,” and authorities believe more than one person fired shots, said Glendale Police Department spokesperson Jose Santiago. Between 200 and 300 people were in attendance at the outdoor venue when the shooting broke out.

Santiago said multiple people were being questioned Monday, but no arrests had been made and police are still searching for other possible suspects.

“Our detectives are trying to narrow down the scope of how many shooters we are dealing with,” Santiago said.

The police department identified the dead as brothers Damien Anthony Sproule, 17, and Christopher Juaquin Sproule, 21, as well as Milo Christopher Suniga, 21.

The wounded included a 16-year-old boy who was critically injured and required surgery overnight, but Santiago said he was expected to survive. Other people between the ages of 20 and 23 were injured.

In a statement Monday, the restaurant said it was cooperating with the police investigation while trying to make sense of a “heartbreaking event.”

“Our hearts go out to the victims, their families, and all affected by this senseless violence,” the statement said.

Social media videos shared by the restaurant earlier Sunday before the shooting showed people dancing near a stage with a DJ booth.

Santiago said event organizers removed a group of people from the venue after they started fighting near the stage. They began shooting at each other just outside of the event, Santiago said.

Bystander Lupe Rodriguez said he ran to safety when he heard the gunshots. He was shaken, but said he was grateful that he and his friends survived.

“There was a man on the ground, and it didn’t look like he made it,” Rodriguez said. “His father was yelling out his name.”

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This story has been updated to correct that the age of both the deceased brother and the other adult victim is 21, not 29, based on new information from the Glendale Police Department.