Officers arrived to find one person with a gunshot wound and took that individual, who was expected to survive, to a hospital, Harris said.
The mall was locked down and surrounded by officers and a SWAT team responded to the location, according to Harris.
The suspect left the scene, Harris said, but officers systematically searched the mall for additional possible victims and escorted people from the premises.
"There are no known additional victims at this time," he said.
Detectives initially described the man as a 20- to 25-year-old man with a shaved head and wearing a black shirt and checkered shorts, Harris said.
Video posted on Facebook showed the male shooting victim, who appeared to be bleeding, being cared for by other people inside the mall just north of the food court on the main level, outside a Build-A-Bear Workshop and Finish Line athletic apparel store.
Madrona Middle School, which is located near the mall, was placed on lockdown after the shooting, amid concerns the suspect may have gotten out of the facility and run in the direction of the campus.