The incident, which investigators described as "a mechanical failure," occurred at approximately 7:25 p.m.
"(It is) what I call a freak accident," said Robert Dallian of the Kemper Development Company, which manages the mall.
A witness told KOMO News she heard a loud sound followed by chaos near the escalator. When she went toward the noise, she saw that chunks of the escalator had fallen off.
Fire Lt. Troy Donlin said a man in his 30s suffered a minor injury. Three other people were transported for precautionary checks. They included a woman in her 30s and two 3-year-old children.
Donlin said investigators were still trying to piece together the incident.
"We're not sure how many people were on the escalator when the incident occurred, nor are we sure where they were on the escalator," he said. "Most of the damage is at the top of the escalator."
Nicole Johnson said the incident set off confusion among the crowd that had gathered for the Snowflake Lane celebration.
"There were hundreds of people around here, so it was just chaos of people just walking in, going back to their cars," she said.
The cause of the incident was not immediately clear. The escalator had been installed in 1982 and maintained regularly since by the company Schindler. The state escalator inspector had been alerted, and an investigation was expected.
The store remained open during the incident.