Or someone else might attend to it:
Recently, a man was arrested for ejaculating into a female coworker's water bottle on two different occasions. Once would have been bad enough, and he at least could have chosen something a little more inconspicuous to masturbate into like, oh I don't know, Sobe's popular coconut flavored drink "Lizzard Blizzard"? Anyway, the unfortunate female coworker unknowingly drank the infected water and fell ill both times, showing above all else that the guy really needs to re-think his eating habits. The second time she fell ill she decided to send in the water bottle to a lab for testing. They not only found the semen but somehow matched the DNA back to the offender and were able to bring him to justice.
More stories of public/horrific masturbation—including a pastor who got caught masturbating in the boy's underwear aisle at a dollar store—here.