Seattle police are seeking the public’s help in identifying a suspected serial masturbator who publicly pleasures himself while disguising his identity with a makeshift ninja outfit.

Cops first learned of the masked pervert in January, after a woman called 911 to report that a man was “masturbating outside the front door of her home.” Cops responding to the scene were unable to locate the suspect.

Last month, a night vision camera outside the woman’s residence recorded the suspect again pleasuring himself next to the front door. As seen above and below, the surveillance images--which captured the masked masturbator in the act--show him dressed head-to-toe in dark clothing (the night vision camera makes dark colors appear white).

Residents of the targeted home are University of Washington students who say that they have “heard suspicious sounds outside their house on several occasions,” according to cops. Investigators believe that the masked masturbator may have been at the residence four times over the past several months.