Police in Glendale, Arizona said three people died and five were injured after shooting at a restaurant Sunday night. No one was arrested, but investigators believe they were involved in multiple shooters.

Glendale Police Department spokesman Jose Miguel Santiago said Monday that the shooting stemmed from a battle between at least two groups of people from El Camaron Gigante, a steakhouse and location in the city's downtown area is located at the police headquarters. It happened around 7:45 pm as the Cinco de Mayo event is over.

Officials said on Monday that they believed the shooting was an isolated incident between people they knew each other and did not appear to be any lingering danger to the public.

Police said it is not clear what caused the fight or gunfire. San Diego identified the murdered people as three 17, 21 and 29 years old. The teenager and the 29-year-old are brothers. Police said they would not release their names until they were received.

Some of the injured in the shooting were hit by shrapnel, according to police. They were identified as 20-year-old women, a 21-year-old woman, a 20-year-old man, a 23-year-old man and a 16-year-old boy. San Diego said the teenager is undergoing surgery to treat the injury and is expected to recover completely.

Lupe Rodriguez, a bystander in the shooting, told CBS Phoenix branch Kpho-TV that he had to be safe when the gunfire began. He was shocked by the experience, but he and his friends were grateful.

Rodriguez said to the station: "I heard people yelling." His father yelled his name. This is awful. ”

one May 5 According to the Facebook page on Sunday afternoon, a party was held at El Camaron Gigante from 1pm to 8pm on Sunday. The brand promotes the event as a "family friendly celebration" which includes "music, low-class people and good resonance". Its Instagram story features dozens of video clips and images that seem to show the crowds of attendees eating and dancing at parties throughout the day.

San Diego said the fight started initially between people near the stage at the concert. They were escorted to the parking lot, fighting escalated and resulted in a shooting.

El Camaron Gigante spoke in a statement shared on social media on Monday.

"We are shocked by the tragic shooting that took place in the parking lot outside the restaurant on May 4. Our hearts are for the victims, their families and all of this meaningless violent impact," the statement said. "We are working closely with law enforcement and supporting our team as we handle this heartbreaking event. Thank you for your patience and respect together in our grief and staying in touch with the community."

On Sunday afternoon, the shooting has not been publicly resolved. CBS News contacted the brand for comment.