A masked gunman opened fire at Clackamas Town Center, a mall in suburban Portland, Ore., killing at least two people before he was killed himself, police said.
"This is no longer an active shooter," Clackamas County Sheriff's Office spokesman Lt. James Rhodes said. "I believe the shooter has been neutralized and we are securing the mall, securing the scene and treating the wounded."
There was not an exact count of those killed or wounded, he said.
"We know there are multiple wounded," Rhodes said. "Lifeline has landed to treat at least one of those wounded and we're set up to treat them as we find them as we search the mall."
Hundreds of people were evacuated from the busy mall full of holiday shoppers after the shooting began at around 3:30 p.m. PT.
Witnesses described seeing a gunman who looked like a teenager with a white hockey mask, wearing what was believed to be a black, bulletproof vest and carrying an assault rifle. Police confirmed the shooter was a man, though they would not give his age or other details yet.
The person entered the mall through a Macy's store, ran through the upper level of Macy's and opened fire near the mall food court, firing multiple shots, one right after another, with what is believed to be a black, semiautomatic rifle, according to witness reports.
Katie Tate said she was in the parking lot of the mall when she saw the shooter run by, wearing a mask and carrying a machine gun, headed for the Macy's.
"He looked like a teenager wearing a gun, like a bullet proof vest and he had a machine, like an assault rifle and a white mask and he looked at me," she said.
Witnesses described the shooter as being on a mission and determined, looking straight ahead. He then seemed to walk through the mall toward the other end of the building, shooting along the way, according to witness reports.
Those interviewed said that Macy's shoppers and store employees huddled in a dressing room to avoid being found.
"I was helping a customer in the middle of the store, her and her granddaughter and while we were looking at sweatshirts we heard five to seven shots from a machine gun fire just outside my store," Jacob Rogers, a store clerk, told ABC affiliate KATU-TV in Portland.
"We moved everyone into the back room where there's no access to outside but where there's a camera so we can monitor what's going on out front," Rogers said.
Evan Walters told ABC News Radio that he was locked in a store for his safety and he saw two people shot and heard multiple gunshots.
"It was over 20, and it was kind of surreal because we hear pops and loud noises," he said. "We're next to the food court here and we hear pops and loud noises all the time, but we don't -- nothing like that. It was very definite gunshots."
Police are still searching the mall for any remaining survivors.