The shooter, identified as 19-year-old Santino William Legan, appeared to randomly target people with an “assault-type rifle” on the last day of the Gilroy Garlic festival Sunday, according to Gilroy Police Chief Scot Smithee.
The dead included a six-year-old boy, a 13-year-old girl and a man in his 20s. Twelve other festival-goers were wounded in the attack.
Smithee told reporters Monday that police responded in less than a minute of the shooter opening fire.
“It could have gone so much worse so fast,” he said.
Authorities said they were searching Monday for a possible second suspect, following unconfirmed reports by eyewitnesses that Legan may have had an accomplice.
The food festival, in the agricultural city of Gilroy about 170 kilometers (106 miles) southeast of San Francisco, had security that required people to go through screening with metal detectors and bag checks. Police say the shooter cut through a fence to avoid the security checks.
Police believe Legan legally purchased his weapon in Nevada this month. They say his motive is still not known.
President Donald Trump on Monday expressed deep “sadness and sorrow” over the incident. “While families were spending time together at a local festival, a wicked murderer opened fire and killed three innocent citizens, including a young child. We grieve for their families,” he said.
California Governor Gavin Newsom said in a tweet that he was grateful for the police response to the shooting and called the attack “nothing short of horrific.”
The three-day garlic festival attracts around 100,000 people each year and features food and drink, cooking competitions and live music.
Smithee said the festival relies on thousands of volunteers each year and raises money for various organizations in the community.
“I think that the number of people that are willing to give their time for the betterment of other people is a wonderful thing. It is just incredibly sad and disheartening that an event that does so much good for our community has to suffer from a tragedy like this,” he said.