Looking down at our joined hands, I said, "your magical overload caused a tremendously powerful outburst. That much was obvious. But anyone who was close, would have had their bodies vaporized by the power of the magic." It’s happened before, when I dismantled the curse when it was heading towards Harry. The Killing Curse was a tremendously powerful spell, possibly one of the most to be casted without outside help or rituals. It derived so much from emotions and the magical core, it could cause tears in the soul. If you add on committing the most devious act, it would easily allow one to create a Horcrux. 