STORY: He identified the suspect as Huu Can Tran, 72, who wielded a pistol with a high-capacity magazine.
"We want to know, we want to know how something this awful can happen," Luna told reporters.
Luna said Tran turned a handgun on himself on Sunday morning as police approached a white van he was driving in Torrance, about 20 miles (34 km) from the site of the shooting at the Star Ballroom Dance Studio in Monterey Park.
Five of the victims were male and five were female, Luna said. Their identities have not been made public. Another ten people were shot, and seven of them remain hospitalized, with at least one person in critical condition, authorities said.