Three women have been shot dead and a man critically injured at a shopping centre in Burlington, Washington state.
Police have released a picture of the suspected gunman, who fled the scene armed with a rifle.
The Cascade Mall and nearby shops have been evacuated and police have asked the public to stay away. The motive for the attack is not clear.
The suspect, described as a “Hispanic male wearing grey,” was seen heading towards the Interstate 5 motorway.
Washington State Trooper Heather Axtman told the BBC that the fatalities had taken place inside Macy’s department store.
Police originally said four people had died but later revised the toll to three women dead and one man critically wounded with one woman suffering non-life-threatening injuries.
Washington State Patrol spokesman Mark Francis said on Twitter that emergency medical teams had entered the shopping centre “to attend to injured” and that people were being evacuated to a nearby church.
It was initially thought more than one person could have opened fire in the shopping centre, but Mr Francis later said they believed “just one shooter” was responsible.
Mr Francis said the gunman had left the scene before police arrived.
Emergency management officials have told people to avoid the area near the Cascade Mall and drivers are being urged to keep nearby major roads clear.
Burlington is about 65 miles (105km) north of Seattle.