A 15-year-old has been detained in connection with Sunday’s deadly shootout at the Seattle Center that involved at least two others — one of whom was killed, The Associated Press reported.

Police said in a document filed in juvenile court they believe there were at least three shooters: the 15-year-old, an acquaintance who died at the scene, and “at least one other unknown suspect,” according to the AP.

Nicole Powell, the Seattle Police Department’s assistant chief of investigations, said during a news conference Monday afternoon that investigators believe the shooting, which left three dead, may have been gang-related, with two groups firing at each other. The deceased shooter was 19, and a 56-year-old woman and 44-year-old man were also killed.

“Based on the evidence at the scene, investigators believe” the 15-year-old “and one of the deceased engaged in a gunfight with at least one other unknown suspect,” the document filed in court said, according to the AP.

Authorities earlier said they believed two people were shooting at each other, according to Seattle Assistant Police Chief Tyrone Davis, who said there is no ongoing threat to the public.

There were at least seven victims caught in the crossfire, possibly eight, authorities said in a Monday news conference.

The King County Medical Examiner’s Office on Monday identified the dead as Carlos Israel Sanchez Villalba, 44; Ashley Whitehead, 56; and Junior Cee Niko Semo, 19, according to the AP.

Villalba was a husband and father of three known for his kindness and willingness to help others, according to a GoFundMe campaign launched Monday to help his family with funeral expenses, the AP reported. He died from a gunshot wound to his torso, according to the medical examiner’s office.

Four wounded included a 2-year-old boy, who was in satisfactory condition Monday. The others — two men, ages 23 and 27, and a woman, 39 — were discharged, a hospital spokesperson told the AP.

One of the victims was walking a bicycle when struck, the court document said, according to the AP. The toddler was with his mother.

Police are asking for those with information about the shooting to come forward.

The shooting at the Bite of Seattle, a free event that draws hundreds of thousands of guests each year, sent attendees running for their lives. A large group was seen knocking down a fence to escape after a volley of gunfire, the latest gruesome entry in the ever-expanding log of Americans victimized by gun violence while doing everyday activities.

Authorities responded to reports of shots fired just after 6 p.m. at the Seattle Center.

“There were about six or seven, multiple gunshots,” Justice Beitzel, who was eating with friends as a concert played nearby, told CNN’s Ben Hunte. “All of a sudden, I just saw people running towards us.”

Two people were declared dead at the scene. Another person died after being taken to a local hospital, Davis said late Sunday.

In emergency dispatch audio obtained by CNN, one person was heard requesting a “small child tourniquet” for a victim at the scene.

The 2-year-old boy was taken to Harborview Medical Center, the fire department said Sunday. By Monday morning, the toddler remained at the hospital in “satisfactory condition,” according to Susan Gregg, the hospital’s media relations director.

A few other victims were seen at local hospitals, including the 23-year-old man and 39-year-old woman, who have since been discharged from Harborview, and the 27-year-old man, who was released from nearby UW Medical Center – Montlake, Gregg added.

Police recovered two weapons at the scene.

Police said the 15-year-old suspect, who surrendered on scene, was booked into the Judge Patricia H. Clark Children and Family Justice Center on investigation of firearms violations and first-degree assault.

A judge ordered the 15-year-old held in juvenile detention for investigation of firearms violations and first-degree assault. The King County prosecutor’s office said it expected to receive the case from Seattle police on Wednesday for a charging decision.

Police have not formally arrested anyone for investigation of homicide in relation to the shooting, Barnes said.

The shooting is one of at least 271 mass shootings in the US this year, according to the Gun Violence Archive, which defines a mass shooting as one in which four or more victims are shot.

The Seattle Center spans a 74-acre campus and is home to the Space Needle and the city’s largest arena, drawing more than 12 million visitors each year. And hundreds of thousands of those visitors bring their appetites to the center for the annual Bite of Seattle Festival, which hosts hundreds of local vendors offering creative foods and live entertainment across three days.Seattle Center

Crowds of people walked through the aisles of outdoor vendors Sunday, passing plates of poke, bowls of noodles and freshly grilled seafood. Social media users gleefully documented their cheese pulls and noodle swirls in videos shared online.

As shots were fired, the jovial mood turned to panic. Festival-goers rushed to flee the danger.

A livestream from food vendor Hawaiian Honey Cones captured a man speaking to the camera as at least four gunshots rang out in the background.

People ducked and ran from the scene as a large group of attendees knocked down a fence on their way out of the area.

In the aftermath of the chaos, witnesses shared varying accounts of what they saw and heard.

Two witnesses told CNN affiliate KOMO they heard seven to eight gunshots, as people ran in all directions. Another attendee said he was near a stage where a band was performing, when he heard at least two dozen shots.

Another man said some people didn’t react right away, thinking, “Oh it must be fireworks or something.” But after more shots were heard, he saw people “storming through the area” trying to get out.

Some people appeared to take shelter in the gift shop of the Space Needle at the Seattle Center, video shared with CNN showed.

Police, emergency responders and officers from several agencies, including the FBI, were at the scene afterward, video showed.

A Washington state SWAT team was also on its way to assist at the request of Seattle police, Gov. Bob Ferguson said.

CNN has reached out to Seattle police and city officials, as well as the Seattle Center, the FBI, and the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Seattle Mayor Katie Wilson called the shooting “an act of horrific violence” and said the community “is trying to understand how a gathering built around culture, connection, and joy ended in gunfire.”

“In the days ahead, we will establish what happened and be transparent with the public about what we have learned,” Wilson wrote. “Tonight, our attention belongs to the people whose lives were taken, those fighting to recover, and the families beside them.” (CNN)

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