Police say they started getting calls in December from angry Craigslist users saying a man was buying iPhones and iPads with counterfeit money.
In each of those cases, the seller didn't realize the money was fake until the buyer had already left with the electronics.
In all, police say the same man fleeced 12 people in both King and Snohomish counties.
After joining forces with the Kirkland Police Department and special agents with the Secret Service, detectives caught a break in the case when one of the victims picked out a suspect using a photo line-up. Police knew the man from a 2011 counterfeiting case.
Officers soon tracked the man down in Lynnwood, and when he took them to his Everett apartment, they found more counterfeit money and equipment to make the money.
The 21-year-old man was booked into Snohomish County Jail. He has yet to be charged.