City police spokeswoman Kathy Lowe said a 42-year-old man was arrested by bike patrol officers in the parking lot near the Macy's department store at the Fashion Island mall, the Los Angeles Times reported.
Deputy Chief David McGill said more than 50 shots were fired and a handgun was recovered at the scene. The shots were apparently fired either in the air or at the ground, and no one apparently was wounded, police said.
The newspaper said many shoppers posted messages on Facebook and Twitter describing their circumstances.
Shopper Dena Nassef told the Times she and another person were walking toward Macy's about 4:30 p.m. when people started panicking.
"With what happened in Connecticut, we were freaking out," she said. "It was like crazy people leaving stores."
Nassef said some people laughed, apparently not believing the situation was serious.