Riding a Brooklyn-bound 4 train, amateur photographer Kate Black noticed a man "pitching a tent" and "thrusting his hips" in ladies' faces. Thinking quickly, Kate photographed him, then declared a jihad against the pervert on her Flickr page.

Here's how Kate describes her encounter with the rogue penis thruster:

I missed getting a shot of a subway masturbator's face today, but here's his back. Light skinned black male, late 40s, short hair with some gray. Wearing blue workman's jacket w/ white script embroidery on the front. This was taken on Sunday on a Brooklyn-bound 4 train. He exited at Nevins Street.

He saw two single women (myself and a young woman across from me) in a not very densely populated train car, and entered from an adjacent car while the train was in motion. Wearing sweatpants and pitching a tent. He stood next to/over the young woman across from me, facing me and thrusting his hips out. When he realized I had my camera trained on him, he quickly crossed to stand next to me with his back to me. (Thus pointing his boner at a mom and toddler nearby.)

I am quite certain that this would've escalated had I not had a camera.

Let this be a lesson to you to ALWAYS change your ISO settings as soon as you go from bright daylight to indoor or underground shooting conditions. If I'd done that, I would've been fast enough to get a photo of his face.

And if you know this guy, turn his ass in to the cops. If you don't believe in "snitching," turn his ass in to a bunch of BARD freshmen.

By email, she adds that she's still beating herself up for not getting an identifying photo of the Nevins Street masturbator. "I'd love for him to get arrested for this," she notes.

He put on the hat and dark glasses after he moved and put his back to me. I got a good look at his face and hair when he came through the doors of the train car.

The blue & white cloth hanging from his messenger bag appears to be a pair of those awful tearaway trainer pants, which he may have had to make a quick change if/when he got busted.

Do you know who this masturbating gentleman is? Has the Nevins Street masturbator ever brandished an unwanted phallus in your direction? Send us your photos, or post them below. Or even better, send us his mug shot when he finally gets arrested.

[Images via thekateblack's Flickr]