Lt. James Rhodes of the Clackamas County Sheriff's Office said the unidentified gunman fatally shot two people and wounded a third at the Clackamas Town Center before he died, NBC News reported. Rhodes did not say how the gunman died.
Rhodes told The (Portland) Oregonian the shooter had been "neutralized." He declined to define what that meant, though the newspaper said there were unconfirmed reports the shooter took his own life.
Rhodes said he believed the gunman acted alone.
Police were clearing employees and shoppers who had hidden inside the mall.
Taylor Gibson, 20, an employee at Build-A-Bear workshop on the mall's lower level near Macy's, told the newspaper she was walking toward the front of her children's store about 4 p.m. when she heard shots.
"Me and the others raced to the back of the store and got our customers in the back room," she said.
Mario Collaco, 20, who works in a kiosk at the mall, said he heard about five bangs in succession coming from the second level of the food court. He said the shopping center wasn't particularly crowded, but some people "were freaking out quite a bit."