I wasn't at the barn to smell it, I'm guessing it was ozone, with a static build up in the barn, it has a metal roof and metal bars between each stall. In the aviation world we don't call them lightning strikes, we call them "static discharges". When flying through a highly charged thunder cell the airplane will build up a static charge. There are static wicks on the tip of each wing, tail, and elevator, which are designed to disipate the charge before it builds up too much.

But, sometimes when the rain is very heavy and the cell is highly charged, they cannot dispate the static fast enough and "BANG" you get a large flash and big bang like a shotgun going off. Scares the crap out of the passengers. But a no-kidding lightning strike is quite rare, mostly because we stay the hell away from big thunderstorms!

I'm no expert but I've seen several TV programs on lightning. Some say it actualy starts from the ground up, when a large static charge is built up by the negative ions in a heavy rain/thunderstorm. That's why sometimes people can feel the static and smell the ozone just before the static discharge.