OAKLAND (CBS SF) — Two warring gangs from San Francisco appear to be responsible for a mass shooting at Lake Merritt on Saturday, Oakland police said on Monday.

Police Chief LeRonne Armstrong said his investigators were working with San Francisco police to find those responsible for the shooting a crowded event at Lake Merritt. One person was killed and eight others were injured; Armstrong said it’s believed the same group is responsible for multiple recent shootings.

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“We believe this was directly related to group and gang violence and group and gang violence not even connected to the city of Oakland,” said Armstrong. “This appears to be group and gang violence related to the city of San Francisco.”

There were about 10,000 people all around Lake Merritt for several different events, with some 5,000 people in the area where the shooting happened. The event was a day-long gathering to commemorate Juneteenth.

The victims ranged in age from 16 to mid-60s; the deceased victim was a 22-year-old man from San Francisco.

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Armstrong said most of the people involved in the shooting were from outside Oakland and investigators are looking for more than one shooter.

“Our homicide investigators have determined that the individuals responsible were multiple shooters, not just one,” said Armstrong. “We’ve learned over the last couple of days that several people fired weapons during this event.”

Armstrong also said the large crowd made it difficult for first-responders to get to the victims initially and evacuate them to hospitals, although he said there were a number of citizens who stepped up to open up traffic and allow emergency crew access.

Oakland Police Lt. Leo Sanchez said while some of the victims had been specifically targeted in the shooting, other victims had no connection to the gang activity.

“This investigation is still in its early stages, but I think some of the individuals who were shot and are injured — including the individual who unfortunately passed away — I believe were targeted individuals. Those are the individuals who appear to have some gang or group connections with San Francisco,” said Sanchez. “There are individuals also just part of the festivities, part of the gathering and caught up in crossfire as well.”

Two individuals running from the scene were detained by police and found to be carrying weapons, but neither was associated with the shooting. Armstrong said they were just two of the many who brought guns to Lake Merritt that day.

“There were several armed individuals out there; armed with firearms and prepared for conflict,” Armstrong said. “We continue again in the city of Oakland to see far too many guns, particularly people willing to use guns in our city. And Saturday’s event was one people came armed for, unfortunately.”

Sanchez said no one has yet been identified as a suspect. Community members have been offering bits of information to investigators and some surveillance video is being analyzed, said Sanchez.