An officer spotted a man who matched the description of the suspect just before 4 p.m. and, after a short foot pursuit, arrested him at 6th Avenue and Martin Luther King Way in Tacoma.
Female business owners in Tacoma had been using Facebook to warn each other about a sex criminal who had committing lewd acts inside their stores.
The man's modus operandi was to enter a store run by a woman and quietly knock merchandise to the ground. When the woman would bend down to pick up the item, the man would walk behind her and masturbate.
The owner of a Tacoma antique store who was victimized by the man had no idea anything had happened until a customer pointed it out.
"As I walked past, the gentleman goes, 'Ma'am, I don't know if you know it, but you have something all over your back,'" she said.
The suspect, who has not been identified, was booked into jail and is facing two counts of assault, according to police.