Four people have been shot dead at a mall in northwest Washington state and the gunman has fled the scene, police said on social media.

The shooting occurred at about 7:30 p.m. local time Friday at the Cascade Mall in Burlington, Washington, about 65 miles north of Seattle, Washington State Patrol spokesman Mark Francis said in a Twitter post.

A local hospital told a CBS affiliate that it has received one causality from the shooting.

Francis said police were actively searching for the shooter, who had posted a photo of rescue workers outside of the mall.

"EMS starting to enter to attend to injured inside mall with police escort and after initial clearance," Francis said in a Twitter post.

The shooting comes less than a week after a man stabbed nine people at a mall in central Minnesota before being shot dead. The FBI is investigating the attack as a potential act of terrorism.