A 72-year-old gunman killed himself when approached by police on Sunday, about 12 hours after he had carried out a Lunar New Year massacre at a dance club that left 10 people dead and another 10 wounded.
The gunman tried to carry out another shooting at a separate club just minutes after the first one on Saturday night, but authorities said two bystanders wrestled the man's weapon away from him before any shots could be fired.
He fled that scene.
Los Angeles County Sheriff Robert Luna identified the suspect as Huu Can Tran, a septuagenarian he said used a high-capacity magazine pistol to shoot up a ballroom dance venue popular with older patrons in Monterey Park, about 7 miles (11 km) east of downtown Los Angeles.
Investigators did not yet know a motive, although gun violence is frequent in the United States.
Luna did not identify any of the victims but said the five men and five women appeared to be in their 50s, 60s and beyond.
The sheriff said the pistol Tran used appeared to be illegal in California, where state laws ban any magazine holding more than 10 rounds.
'We want to know, we want to know how something this awful can happen,' Luna told reporters.
After police say Tran carried out the shooting in Monterey Park at about 10 p.m.
PST Saturday (0600 GMT on Sunday), he was confronted by bystanders at a second dance club in the neighboring city of Alhambra about 20 minutes later, Luna said.
Biden Orders to Lower US Flags for Victims President Joe Biden offered his condolences to the victims of the mass shooting, while acknowledging the impact on the Asian American and Pacific Islander community in a statement on Sunday.
He ordered all US flags at public buildings to be flown at half-staff to honor the victims.
Biden directed that flags be lowered until sunset on January 26 'as a mark of respect for the victims of the senseless acts of violence perpetrated on January 21, 2023, in Monterey Park, California,' a White House statement said.