OAKLAND -- The San Francisco Bay area was reeling Sunday from at least 10 murders over the weekend, including the slayings of at least three teenagers and a bystander cut down in a barrage of bullets.

The killings began late Friday, with four weekend homicides each under investigation in San Francisco and Oakland and one each in Richmond and North Richmond, police said.

Catherine Gulley, 53, died when gunmen opened fire on a group of North Richmond partygoers late Saturday. Police said she was not likely the intended target.

Officers discovered two bodies Saturday morning along a road in San Francisco's Bayview-Hunters Point neighborhood. The pair were identified by the medical examiner as Chris Garcia, 16, of Daly City, and 15-year-old Gregory Jones of San Francisco.

On Saturday night, authorities said, Jose Santillian, 19, of San Francisco was fatally stabbed in the back in North Beach.

The murders come as several Bay Area cities wrestle with chronic violence, especially Oakland, which saw homicides surge nearly 60 percent in 2006.