I don't think anyone really thinks it was a prank. However, the speculation over the muslim origins is now getting mindless. There are muslim terrorists, agreed. However, it seems that too many on FR seem to have forgotten that Klebolds and Harris's walk among us as well, and they can be just as deadly.
I'm not 100% convinced there is necessarily a Muslim terrorist connection, but I am convinced there is some kind of terrorist connection that is being covered up (whether Muslim, Ecological, Anti-jock, White Supremacy, I've no idea UNLESS the Muslim "rumors" pan out).