A shooting Monday afternoon inside one of the nation's largest malls prompted a lockdown of the Southern California shopping center and a massive police response as dozens fled.

Police believe the attacker left the sprawling Del Amo Fashion Center in Torrance, south of Los Angeles. Officers found one person with a gunshot wound inside the mall and don't believe there are additional victims.

Videos taken by people inside the mall and broadcast on TV show a group gathered around the presumed victim, who appeared to have been shot in the upper chest or shoulder. The videos show blood splattered on the floor as officers and mall patrons aid the victim, who appears to be conscious.

Other videos show first responders taking the victim through the mall on a stretcher.

"As of now, it does appear to be an isolated incident," Torrance Police Sgt. Ron Harris said at a press briefing outside the mall.

It was not immediately clear if the shooter was a shopper or employee, or where the person opened fire, Harris told The Associated Press.

Harris said the victim is expected to recover.

TV footage and social media posts also show shoppers and employees evacuating as officers in SWAT vehicles arrived, while others were forced to wait inside for a police escort to leave.

Police methodically searched hundreds of stores and finished the 6 1/2-hour hunt Monday night without finding the gunman, Harris said.

Authorities were also speaking to witnesses and "scouring" video, he said.

Alba Mejia, an employee at the Panda Express, told ABC7 she suddenly saw about 100 people running before she heard shouting.

"I heard somebody say, 'somebody has a gun, somebody has a gun!'" she said. "I didn't know what was going on."

Mejia said she and others tried to leave the mall as an alarm sounded.

"It was kind of confusing and chaotic," she said.

She said she heard the shooter was still on the loose about a half-hour later.

"It was a very scary feeling," she said.

It's unclear when the mall will reopen.

The suspect was described as a man between 20 and 25 years old with a shaved head, wearing a black shirt and checkered shorts.

The shooting prompted the lockdown of a nearby middle school.

The mall has more than 250 stores. A spokeswoman for the mall's owner, the Simon Property Group, referred media inquiries to police.