This happened a few years ago when I was stationed in southeast DC. I used to go for a run that took me down the National Mall, around the Lincoln Memorial, over to Arlington and back.
One night I went running with a buddy. He was dangerously crazy.
It was the Monday of the MLK holiday weekend, I think. On our way back, my buddy came to a stop on the mall. He had to take a leak, he just whipped it out and started pissing right there.
It wasn't that late, maybe 8 pm, but the mall was deserted. We were at a more or less dark place in front of the natural history museum, I think. At the time, the grassy parts of the mall were fenced off so access to the path we were running on was limited and we could have seen anyone coming towards us long before they could see what we were doing. So I turned away and took a piss, too.
When I finished my piss, I looked back at my buddy. Like I said, he was crazy. He wasn't pissing any more, he was jerking his hard dick.
Seeing him jerk off right there out in the open I got hard too. I tucked the waistband of my shorts under my balls and started jerking off too. It wasn't a cold night, we were wearing shorts not sweatpants, the cool night air on my dick and my balls felt good.
We sat back on a bench side by side. I never jerked off with another guy before. I had done it outdoors many times but never so completely out in the open like this. It was incredibly exciting and it felt so good.
We kept jerking off for a while, it must have been twenty minutes or so. I backed off a few times when I was almost about to cum. I could tell my buddy was doing that too.
Finally my buddy pulled his shorts and jockstrap down around his ankles, stood up bare-ass and shot his wad. I dropped mine too, stood up and came in a massive orgasm.
We fell back on the bench and sat there for a few minutes breathing heavily and playing with ourselves a little. Then we pulled up our shorts, got up, adjusted ourselves and started running again. My legs were a little wobbly at first.