According to troopers, the shooter left the scene before police arrived.
The names of the dead were not immediately released.
Tari Caswell told the Skagit Valley Herald that she was in the Macy's women's dressing room when she heard "what sounded like four balloons popping, and I thought that was strange because I hadn't seen any balloons."
“Then I heard seven or eight more, and I just stayed quiet in the dressing room because it just didn’t feel right. And it got very quiet. And then I heard a lady yelling for help, and a man came and got me and another lady, and we ran out of the store.”
Stephanie Bose, an assistant general manager at Johnny Carino's Italian restaurant near the Macy's, told The Associated Press that she immediately locked the doors to the restaurant after hearing about the shooting from an employee's boyfriend.
"He was trying to go to the mall and people were screaming," she said. "It was frantic."
She said he could see police at the doors with assault rifles and said they were no longer guarding the doors as of 9:30 p.m.
Brandi Montreuil told CNN she was at the movies when attendants told them to leave. "I didn't know anything," she said. "The theater attendant came in and apologized for stopping the movie and said they (theater staff) were asked to have everyone leave immediately."
Doc Barron, who had been teaching a boxing class at the mall, told the Skagit Valley Herald that he heard a commotion outside and a bunch of people yelling and screaming for help.
“Someone ran by and said, ‘There’s an active shooter in the mall,’ and told us to lock our gate,” said Barron, who was able to get out of the mall and was interviewed in the parking lot.
The Cascade Mall is an enclosed shopping mall that opened in 1990, according to the mall's website. In addition to Macy's and the theater, it features J.C. Penney, TJ Maxx, and several restaurants. On its Twitter account, mall officials said the facility would be closed on Saturday "out of respect" for the victims and their families.