Island County Sheriff’s Lt. Mike Hawley said he spotted 20-year-old Arcan Cetin Saturday evening in Oak Harbor, Washington, from a patrol car and immediately recognised him as the suspect.

Cetin was unarmed: “He said nothing. He was kind of zombie-like.”

Police had initially described the suspect as a Hispanic man in his late teens or early 20s.

A Facebook page that appeared to belong to Cetin said he was born in Adana, Turkey, went to Oak Harbor High School and had worked at a grocery store on the town’s Whidbey Island.

In February, he posted a link to a “Call of Duty” first-person shooter videogame practice session (below), in an eery foreshadowing of real world violence he was to perpetrate.

YouTube users posted lewd comments on that page and Cetin’s Twitter page Saturday in response to the mall shooting.

The gunman opened fire with a rifle in the makeup section of a Macy’s department store late Friday, killing four women and a man, according to police.

The FBI office in Seattle said it had no evidence the shooting was terror-related.

The shooter later left the store on foot, triggering an intense manhunt.

A weapon was recovered at Cascade Mall in Burlington, a town of about 8,000 people some 110 kilometres north of Seattle.

“I don’t know what his motivation was to do this,” Chris Cammock, police chief in the larger nearby town of Mount Vernon, told a news conference. “But I certainly plan to find out through the investigation, to the best of our ability.”

The youngest victim was named as Sarai Lara, 16, who survived cancer as a young girl. Relatives named another victim as 52-year-old Shayla Martin, who worked as a Macy’s makeup artist.

“We’re really having a tough time right now,” her sister Karen Van Horn told The Seattle Times.

It was the latest chapter in America’s epidemic of gun violence.

Burlington Mayor Steve Sexton’s voice trembled as he noted that the randomness of gun violence in America -- which causes an estimated 30,000 deaths a year - had hit his small town.

“This was a senseless act, the world knocking on our doorstep. It came to our little community,” Sexton said.

The shooting came amid fierce debate in America over gun control laws. It is a hot issue on the campaign trail ahead of the November 8 presidential election.

The shooter had walked in without a weapon, and appeared on security cameras about 10 minutes later with a rifle, said Cammock.

Police received calls around 6:58 pm Friday that shots were fired at the mall.

The suspect was last seen walking toward a highway from the mall before officers arrived.

The mall was evacuated, police swarmed the area and medics rushed to the scene after the mall was initially placed on lockdown.

Local and regional law enforcement from more than 26 agencies responded to the scene, with about 200 officers on site at the height of the incident.

Police took hours to clear the sprawling building.

“We are devastated by the tragic events that occurred last night at Cascade Mall,” Macy’s said in a statement on its Facebook page Saturday.

At a vigil held for the victims Saturday morning in Burlington’s Maiben Park, Kelly Couture, who exited the mall through a Target store as the chaos was unfolding, told The Seattle Times there were “just sirens and people were yelling and running out of the building.”

The mall was closed Saturday as a mark of respect for the victims.

Additional reporting by Associated Press