The eight seconds after decapitation is how long it takes for the oxygenated blood to leave your head, during which time the brain is still pretty functional. In Bud's case, he caused enough tissue damage that it was probably pretty much lights out for him. And while I do often feel sad for people who think they need to off themselves, there are also some whose suicides I find pretty reasonable, and his was one of them. He made a rational decision and I don't think he had any regrets about it.
It occurs to me that people might just be watching 9 seconds of him shooting himself and slumping over. If people are going to go out of their way to watch him die, I'd hope that they at least watch what he had to say before hand. He spent a few minutes somewhat eloquently explaining himself before whipping out that ginormous ass gun, and I suspect the reason he chose to do it on camera was so that people would pay attention to his message. If nothing else, you can read his final remarks at wikiP.