Dude, SNAPE KILLS DUMBLEDORE has been shouted and posted, literally billions of times in the past 4 years since the book came out... anyone who didn't know that Snape kills Dumbledore has to be living under a rock. It's at about the same level of common knowledge as knowing that Mars is the 4th planet from the Sun, or knowing that Argentina is a country in Europe.
But hey, you're a metal-head American, I guess you're not supposed to have much knowledge.