Police also are asking the public to come forward with any information that leads to the arrests of suspects in the cases.
Frank Gore, 27, of Vallejo, was shot around 9:30 p.m. Tuesday in the rear parking lot of House of Soul Recordings at 777 Tuolumne St. He was pronounced dead at the scene.
Gore's death marked the city's 24th homicide of the year and the fourth in six days, according to police.
Around 3:40 p.m. Tuesday, Anthony Young, 27, of Vallejo, was fatally shot in the parking lot of King's Market at 1624 Fairgrounds Drive.
Police said four law enforcement agencies had to respond in order to contain a large and hostile crowd that gathered at the scene.
Police Capt. Jim O'Connell said Thursday morning that it is not yet known whether the two murders are related. He said the community's help is crucial in cases like these.
"This is a community crisis, not a police crisis," O'Connell said regarding the spate of homicides.
"Our detective and staff are working around the clock to solve them. It's critically important that people come forward. We need help to solve these," O'Connell said.
Five detectives, a detective sergeant and crime scene investigation support staff are working on the homicides, O'Connell said.
"They're doing phenomenal work with the staff we have and the workload," O'Connell said.
"Not every case can be solved with forensic evidence. We know there are people who have personal knowledge of the suspects, who drove them away or confided with them," O'Connell said.
In a separate killing on Friday, police said, 34-year-old Esohe Izevbigie, of Oakland, died at a rap concert when she and another woman were caught in the crossfire of a shooting in the south parking lot of Dan Foley Park. The shooting happened just before midnight, police said.
Izevbigie and her friend were attending a concert by rapper "Lil Scrappy," police said. Izevbigie's friend was treated at a hospital and released.
Multiple vehicles also were struck by gunfire, but the women were unintended targets, police said.
Vallejo police Lt. Kevin Bartlett said different-caliber bullets were found at the scene, indicating that there were multiple shooters.
One of the shooters was described as a black man wearing a tan shirt. He remains at large.
Lil Scrappy is known for his role on the VH1 reality show, "Love & Hip Hop: Atlanta."