Witness Amber 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.
Other 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.
Witnesses told KATU they heard "pops" and then saw the mall Santa fall to the ground. The man dressed as Santa, who did not give his name, told KATU that he wasn't concerned at first by what sounded like balloons popping.
"Then when I heard about 18 more shots, I decided it was a semi-automatic and I hit the floor and my employees must have just scattered and got out of there because when I got up there was nobody there but me," he said.
Others 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 KATU.
"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, an employee of a store in the mall, 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."
Former FBI agent and ABC News contributor Brad Garrett said the shooter's mask is typical for mass shooters, who often dress up in costume or wear something other than their regular clothes when they open fire in public.
"The biggest thing for a mass shooter is the control and empowerment for the shooting," he said. "It isn't uncommon for shooter to wear a costume, or sometimes simply to dress in black. In this case, apparently, he wore a hockey mask. He went there being someone other than who he is in reality because it gives him power."
Garrett called the shooting today one of the worst scenarios for law enforcement, as malls are more crowded than ever during the holiday shopping season.
"The thing about mass shooters is that they almost always are premeditated. They are planned," Garrett said. "This shooter I'm sure went through some period of steps before he actually reached going to mall, and there'll be signs or systems either through friends, online, through relatives that will play into understanding why he committed this act."