Epoxy Hardener Chemicals?

I am an avid model builder, and i recently bought some Extreme Power (R) 5-minute Epoxy, so that i could work with my models, and build them a little quick, without having to wait 24 hours to ensure maximum glue adherence. I followed the instructions, it said harmful, so i was wearing rubber gloves to be perfectly safe. I cut off a little bit of the tops like it said. I then grabbed the hardener, i unscrewed the top to pull out the store safety seal, like the instructions said, and i pulled it out, and almost dropped the bottle. The smell of rotten eggs was quite powerful, and my head wasn't even over the bottle. I was just wondering what chemical(s) were in it that made it smell like that. I whiffed the resin (using the proper way of waving my hand over the bottle to waft the air towards me) and there was absolutely no smell at all, so it must be just part of what makes the hardener....harden the solution. Does anyone know what it is?