The name has been circulating on social media for the last few hours, at first seemingly based on the fact that his Facebook and Twitter pictures looked like the photographs of the shooter on the Cascade Mall security cameras. But multiple reliable sources have now confirmed that Arcan Cetin, 20, originally from Adana Turkey is the suspect now in custody.
Cetin was arrested without incident in Oak Harbor, Washington earlier this evening.
EDIT (10:00 AM CST 9/23/16): I removed Cetin's Tweet referring to his alleged ex-girlfriend, as well as the picture of them together. It appears that she had been previously employed at the Macy's, but she wasn't present in the mall during the shooting, and I have yet to see any evidence confirming the initial rumor that his motive for the murders involved her. As far as I can tell, the incident now appears to have been an attack against random strangers.