A manhunt is under way for a gunman who the police say fatally shot five people at a mall north of Seattle on Friday night (Saturday AEST).

The attacker killed four women in the cosmetics department of a Macy's department store at the Cascade Mall in Burlington, Washington State, the authorities said. A man was also critically wounded in the shooting and transported to Harborview Medical Centre in Seattle, where he died.

The youngest woman killed was described as a teenager, law enforcement officers said during a news conference on Saturday morning local time.

The gunman, who was armed with a rifle, left before the police arrived. The mall was evacuated after the 7.45pm shooting (12.45am Saturday AEST), said Sergeant Mark Francis, a spokesman for the Washington State Patrol.

A spokesman for the FBI's Seattle field office said that there was no evidence to suggest that the shooting was an act of terrorism.

Burlington Mayor Steve Sexton described the shooting as senseless. "There are people waking up this morning and their world has changed forever," he said. "The city of Burlington has probably changed forever. But I don't think our way of life needs to change."

Mr Sexton said: "It was the world knocking on our doorstep. It came to our little community here."

The authorities believe there was only one gunman. He was last been seen walking toward Interstate 5, Sergeant Francis said.

After the shootings, the gunman left the rifle behind, the authorities said. They declined to give details about the weapon or to say how many rounds were fired.

At a news conference, the authorities in Washington described the fearful moments after the shooting as officers searched the roughly 40,800-square-metre mall for the attacker, finding only store employees and shoppers.

The mall remained closed because it was still a crime scene. As of Saturday morning local time, the bodies remained at the store, said the Skagit County coroner, Hayley Thompson. She said she will not be able to confirm the victims' identities until she gains access to the scene.

"I have not had a chance to get any of the information yet," she said.

Police officers entered the mall in teams, unaware during the hours-long search that the gunman had fled before their arrival. They searched "every room and every nook and cranny," said Lieutenant Chris Cammock, commander of the multi-agency response team conducting the investigation.

Security camera footage showed the suspect, who the police described as probably in his late teens or early 20s, entering the mall without a weapon. Footage taken 10 minutes later showed him entering Macy's with a rifle.

Lieutenant Cammock declined to comment on reports that a witness heard a man shout a woman's name. The authorities do not yet know the suspect's motivation, he said.

Governor Jay Inslee offered condolences on Friday night to the families of the victims.

The FBI said early on Saturday that it had "no information to suggest that additional attacks" were planned in Washington state, and that it was coordinating intelligence efforts with the local authorities. More than 200 officers from at least 26 agencies responded to the shooting, authorities said.

Eric Mathews, 40, who was meeting his son at the mall, said it had been a typical Friday night at the mall, about 105 kilometres north of Seattle. He described it as a "teenage scene kind of thing."

Mr Mathews arrived around the time the shooting occurred. He and his son, Kai, 16, left just before the mall was locked down, he said, adding that four of Kai's friends were stuck inside after the mall was locked down.

"Imagine I was late or if he didn't answer his phone," Mr Mathews said, referring to his son. "That stuff is running through my mind."

Stephanie Bost, an employee at Johnny Carino's, a restaurant at the mall, said that after hearing from a customer about the shooting, about 90 metres away, "we went on lockdown."

One woman, Tari Caswell, told the Skagit Valley Herald that she had been in the Macy's women's dressing room when she heard four loud pops followed by seven of eight more.

"I just stayed quiet in the dressing room because it just didn't feel right," she said. "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."

Officials also called off the Burlington-Edison High School football game and evacuated the stadium, which is just north of the mall, The Herald reported.

The attack was the seventh time this year in which at least four people were killed in a shooting in Washington, according to The Seattle Times.

The New York Times