Shooting People Usually Doesn't Fix Things

I've worked in the food industry for about six years. I am definitely aware of how shitty it can be. Between management, bad customers, and being on your feet many, many hours to earn almost a living wage, I have had my share of explosively angry days. I managed to find an outlet in exercise, so I never felt the need to lash out at any one person. I do empathize with Petey though, and his frustrations with Brad the manager. Sometimes it's hard not to believe that a manager's job isn't to drive everyone insane, so I get wanting some sort of backlash, especially after being fired.

What I don't get is his execution. Why shoot him at work? Vulnerability? Irony?
I guess the location makes sense for revenge, but unless Petey was really, really terrible with his gun, I can't fathom why he shot so many other people. Did he blame everyone there for his unhappiness? Why does he shoot the super nice waitress, Karen?
Anyone who considers mass murder as a solution to their problems isn't really in their right mind, so maybe approaching this with logic isn't the best idea to begin with.

On the victim end of this story is an unfortunate woman with a fatal wound to the head, whose parents want to keep her vegetative to finish her pregnancy.
My knee-jerk reaction to that idea was, "Woah, no way," and then moved to whether that was even possible.
Assuming that it was, how would you feel about being kept artificially "alive" in order to "incubate" your unborn child? The whole idea has a weird vibe to it, but after marinating on the idea for a bit, all I can say is why not? If I was already dead, what harm would it be to use my body to finish creating a life? I'm an organ donor so my body can save lives; the only catch here is that an uterus would require way more resources to be habitable for a fetus. If that's the catch, I think I'd still be okay with it. Would you do it?

Season 2 Episode 25 - 17 Seconds