Newbie Q about vibrators, prostates and shooting myself in the eye O.o

Hi all.

As an eager young gay 22 year old, too busy with work to arrange some good old fashioned ass-fuckery...ever, I have started to experiment the last six months with toys for anal and prostate stimulation. My poor ability to choose appropriately sized novice toys notwithstanding, a recent venture has caused me some confusion.

I am very new to using toys, and it usually requires me to set aside quite a bit of time to get any of my toys comfortably in. One of my explorations however, where upon i had been taken my time with a vibrator. Upon removing the vibrator to slip on a sheath to increase the stretch. When i switched on the vibrator for the first time that session, i immediately ejaculated. Very very forcibly. I was lying on my side so i ended up cumming with enough force to graze past my shoulder, face and finish with a splat at the splat at the end of my bed.

WTF was the first thing that came to mind, especially since i did not seem to be any orgasm i was familiar with as i stayed perfectly hard and could continue onto produce my normal sized level of mess afterwards.

Can someone tell what happened? O.o