I can't remember the exact details (other than it was funny as hell), but I know it involved Andy Samburg and Shiloh LaBeouf. From what I could recall, Andy was singing about this letter he was writing and then he said his friend was going to shoot him and it happened; then he shot the friend; then the cops come in and read the letter; it says they will shoot each other and they do; then the sister comes in and sees all the dead people and reads the letter and it says she will get shot; then there is another minute or so of all the "dead" people shooting her repeatedly. (and the whole thing is done in slow-mo with some sad-sounding music in the background)
It may not sound funny, and it probably isn't for some people, but I thought it was (although I had to watch it a second time to get over the shock of seeing it the first time).   See 5 other replies