First Time Flashing

Several years ago I was working for an agency and my office was in NY. About twice a month I had to deliver a load of paperwork to a different agency's offices in the city. I'd either drive myself or get a ride with a colleague, which was always helpful since the area I had to go to was notorious for being a hard place to park and even official vehicles might be towed.
So this was a nice Summer day, probably around 11am and I finished dropping off the papers and was going to take my lunch break there in town.

There were always lots of pretty young women and girls working in the offices nearby and lunch hour was like a fashion show. My friends and I joked about throwing a couple of folding chairs in the trunk of the car so we could just set them up outside one of the big buildings and just watch the girls walk by.

This day I was on my own and after leaving the office where I had business, I stopped at a corner and bought a hot dog and a soda from the street vendor. Did the girlwatching that I anticipated and before heading back to my own office, I went back to the building I'd left earlier to use a men's room. This was a 20+ story government office building that was probably built in the 1930s. Had large elevator lobbies on each floor and two wings of offices branched off the elevator lobbies. The floors were all marble and the building was pretty ornate.
Lots of floors had the lavatories locked and you had to be an employee to have a key.
Someone told me that on the 9th floor the men's room was always open because the lock was broken and they hadn't bothered to replace it for months.

So I went into the men's room and the way it was set up there were three urinals next to the sinks and there were three stalls to the left of the urinals on the opposite wall. I was peeing at a urinal when I noticed there was a guy in the nearest stall. The doors of the stall didn't go all the way down so I could see the guy's feet and his pants down around his ankles as he sat on the toilet. I could also see that the door jamb was a very poor fit with a large gap. As I stood there peeing I heard the guy in the stall cough or clear his throat or something and when I glanced in that direction I could see he was looking through the opening by the door jamb and watching me pee.

I figured the guy was gay or curious or whatever and decided to give him something to look at. Now my dick's just an average cut cock, maybe a bit over six inches but on the thick side. I started to stroke it and got hard quickly. I stepped back from the urinal and made sure the guy in the stall could see my cock and that I was jerking off. I glanced over and we made eye contact and he stayed in the stall while I continued stroking. It was the first time I'd ever had a guy watch me and I was really turned on by what I was doing.
Pretty soon I was feeling like I was ready to cum and I stayed back from the urinal so the guy could see me shoot my load. I shot off probably four or five bursts into the urinal which was about a foot or so away. I heard the guy in the stall kind of groan and I figured he was jerking off too and probably was cumming also.

I quickly slipped my dick back in my pants and flushed the urinal, washed my hands and took off. I didn't want the guy to come out and try to hit on me or anything and didn't want to get caught by anyone coming in to use the men's room.
Got to the ground floor and made my way back to my own office with a nice afternoon ahead and a good cum left behind.