No matter how jackass he was or how drunk he was at the time, i still feel bad for this.
Great entertainer and a funny guy. Jackass aint gonna be the same without him...
Rest peacefully in heaven mr. Dunn.

About the joke part, i dont rly believe that this is a joke (OR i might aswell be wrong and i wish i'd be), seeing how bad Bam Margera took this all on Twitter. And i dont really think, even tho they've made some really messed up pranks, that they would make fun of some of their friend getting into a car accident and dieing.