The incident happened at around 9 p.m. when Oakland police and fire responded to Grand and Euclid Avenues to reports of multiple shootings at a large gathering of about 5,000 people.
Police say the event was peaceful until a fight broke out just after 8 p.m. when an illegal sideshow happened at Grand and Bellvue Avenues. Multiple shots were fired, injuring several people.
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A video provided to ABC7 News by an anonymous source captured hundreds of people running to take cover.
"We have everything from minor gunshots or flesh wounds, to loss of fingers, to some individuals still being in critical condition," said Oakland Police Chief Floyd Mitchell.
Mitchell confirmed there were multiple shooters in the crowd.
"Unfortunately, these fights escalated into multiple people discharging their firearms with more than 50 shell casings recovered at that location," Mitchell said.
We found several bullet holes on a car that was parked on Grand Avenue. This business owner said there was a lack of police presence in the area before the violence.
PREVIOUS REPORT: At least 4 shot near Oakland's Lake Merritt during Juneteenth celebration, police say
"Yesterday they had police cars. They had three to four police cars here during the day and as everything took place last night and got out of control, there was one police car right there at the corner of Grant," said Brad Howard, an Oakland property owner.
Oakland police claimed they had 30 officers on the scene. Howard said the city could've prepared better ahead of time to respond.
"It was their responsibility what took place last night," Howard said.
We questioned them on their response.
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Luz Pena: "You said you did have officers on scene, yet I saw video of the incident, and it looked really chaotic, and I didn't see police officers in that area. You said there were 30. Where were they?"
Assistant Chief. James Beere: "Thirty, but you got to understand, the lake is a significant large footprint within that area. They were spread throughout the area."
The chief pushed back and said this was not the only priority Wednesday night.
Luz Pena: "Would you say you were stretched thin because there was so much going on last night in Oakland that you couldn't actually respond to what was going on in Lake Merritt?"
Chief Mitchell: "No, I wouldn't say that. No, we had people there but you have to understand this is a large city, almost 500,000 people. We had officers there on special detail to provide high visibility there. We also had a shooting incident that Chief Beere just talked about. We also responded to a homicide that occurred prior to that. So, no, we had people there. But to say that we can be at every place at every time, we cannot do that."
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Following the shooting, police said officers tried to guide the crowd into a safe area but some individuals in the crowd punched and pushed officers, resulting in minor injuries.
Another person was injured during an assault that occurred after they walked across the hood of one of the vehicles involved in the sideshow and the occupants' got out and attacked them, Oakland Police Chief Floyd Mitchell told a news conference.
Investigators found more than 50 shell casings at the scene.
At least one gunshot victim was in critical condition. The victims' ages ranged from 20 to 30 years old.
No arrests were made in connection to the shooting, according to OPD. However, one person was arrested for assaulting a police officer.
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According to Oakland police, the Juneteenth-related celebrations in the area were not sanctioned gatherings. The investigation is still ongoing.
The Oakland Police Officers Association blamed the violence toward police on understaffing in the department.
"If city leaders truly value public safety, we need to make serious considerations about adequately staffing the Oakland Police Department," read a statement released by the union Thursday. "Yesterday alone, our officers were stretched thin, handling a homicide, multiple shootings, and an incident involving an individual armed with a rifle in addition to the Juneteenth celebration."
Mitchell said that going forward this summer, Oakland police will request assistance from other law enforcement agencies, and his department will restrict traffic flow in the area of the melee to reduce the opportunity for sideshows. He also said a larger police presence will be planned for the Fourth of July.
"The opportunity to celebrate with your family and friends should never be marred by gunfire," said Mitchell, adding that the department will "work tirelessly" to identify and arrest the suspects involved in Wednesday's shootings.
The Associated Press and Bay City News Service contributed to this report.