The violence began Friday at about 10 p.m. in Long Beach, when two men were shot to death at a birthday party. Then just before 6 p.m. Saturday, a man was hospitalized after being shot by police at a home in affluent Belmont Heights.
Three people were shot dead over the weekend in Compton. And in Pico Rivera, a valet died when a man opened gunfire outside a nightclub.
A woman was killed during a drive-by shooting in Inglewood on Saturday, and in Palmdale, a resident walked out to her backyard to find a man lying dead.
In Hawthorne, a police officer shot a suspected car thief who "jumped from an elevated porch and confronted the officer," Pena said. The suspect's injuries weren't life-threatening.
In Los Angeles, a 25-year-old man was stabbed to death just after midnight Saturday during an argument on Figueroa Street and Pico Boulevard, said LAPD Officer Gregory Baek.
There were also non-fatal shooting in La Puente and Pasadena.
The slayings come at a time when homicides — especially those involving gangs — have declined dramatically throughout the county.
"For whatever reason, it's been a pretty violent weekend," Pena said. "I was thinking, 'For gosh sakes, what's going on here? Is it the last night of summer or what?' "