UNDATED -- The new year in the Bay Area got off to a violent start over the weekend as shootings from Vallejo to San Jose left six dead and several others wounded.

In San Jose, two 17-year-olds were shot to death during a gang-related brawl at a fast food restaurant, police said Sunday.

The boys were shot after two groups of teenagers began fighting about 11 p.m. Saturday at a Jack-in-the-Box, police said.

The names of the slain youngsters were not released. A 16-year-old boy was also shot and injured, police said. The gunmen and the other youngsters with him ran away, according to authorities.

"There's no doubt it's gang-related," said San Jose police Sgt. Steve Dixon. "We believe the victims are gang members or associates, and that's why they were targeted. We believe everyone involved is a member or associate of Hispanic gangs that operate in the area of East San Jose."

Police said there were only about 10 customers in the restaurant when the fight occurred, including the teenagers involved.

The restaurant reopened Sunday, but employees declined comment.

Meanwhile in Oakland, it turned out to be a bloody Sunday afternoon and Monday morning as three men have been killed.

Police say the first man was stabbed to death in the 1900 block of Seminary Road around 3:43 p.m. Sunday afternoon. No suspects have been arrested in that stabbing.

Around 5:45 p.m., police were called to a shooting in the 9600 block of Cherry Street and found two men down on the ground with gunshot wounds. One of the men died at a local hospital, police said, and the other is in critical but stable condition.

At 12:51 a.m. police were called out to investigate a shooting at 673 Capistrano Street. They found an adult male dead at the scene from a gunshot wound. The names of all the victims have not been released.

Oakland police were also investigating a stabbing that took the life of a young man Sunday afternoon.

A police spokesman had few details on the incident, which occurred in the 1900 block of Seminary Avenue. He said the unidentified man was pronounced dead at Highland Hospital.

The violence began in Saturday in Vallejo where three shootings claimed one life and left four people injured, according to Vallejo police.

The first, deadly shooting was reported at 8:19 p.m. Saturday in the 500 block of Porter Street, where officers found 19-year-old Jonathan Leddy lying bleeding in front of a residence, according to a police report.

Leddy was transported to Kaiser Permanente Vallejo Medical Center, where he was pronounced dead at 9:20 p.m.

After finding Leddy, officers followed a trail of his blood to 541 Porter St., where they located three suspects who tried to flee, unsuccessfully. All three were taken to the Police Department for questioning.

The second shooting occurred at 569 Annette Ave. at about 11:15 p.m. Responding officers found Ryan Kennedy, 24, and David Silva, 21, both of Vallejo, suffering from gunshot wounds.

The two were airlifted to Eden Medical Center in Castro Valley, according to police, who did not disclose the mens' conditions.

Police also found a female and a toddler inside the residence. The female was taken to the station for questioning and the toddler was turned over to relatives.

Early Sunday morning, the third shooting occurred near Teeter's Bar at 910 Lincoln Road East. Police responded to the bar at about 1:53 a.m. and found two wounded men, who said they had been across the street from the bar when shots were fired.

Fred Clay, 27, of Fairfield, had been shot in the upper left leg, and 32-year-old Cleo Clark, of Vallejo, had been shot in the foot. Both were transported to Sutter Solano Hospital for treatment.

Officers found spent shell casings at the scene but, despite the large crowd at the bar, no witnesses have stepped forward and no suspects have been arrested.

Police Lt. Ron Jackson said it appears the shootings on Porter Street and Annette Avenue may be related, but police have not yet officially linked the two. Jackson said he does not believe the shooting outside the bar was connected to the other incidents.

In San Francisco, police were investigating a Sunday shooting in the Bayview District.

Police say that the victim, an adult male, was shot once in the chest in the 1600 block of Lane Street around 2 a.m. Detectives do not know much else about the shooting, however, police say, as the victim is refusing to cooperate with investigators.

The man was listed in critical but stable condition at San Francisco General Hospital.