This tragic story strikes me as a normal guy who made a very careless decision while trying to enhance the rock n' roll entertainment for the crowd. Assuming he is not a sociopath, the thoughts that likely torment his every waking moment are probably relentless.
All things considered, I would categorize a robber who stabs someone to death in the commission of a crime to be the worse criminal. This guy didn't plan his night around how he could kill a bunch of people.
~ Blue Jays ~
Or even hurt anyone (assuming, as you say, he's not a sociopath). I agree with your assessment, Blue Jays. It's a terrible tragedy, and I'm sure the families' hearts will ache forever, but according to what you've written, they seem to realize it was an accident and not intentional.