While I'm on the subject...
Thing is, Power Boy was already on the hit list because he comes from Apokolips. As an Apokolipian or possibly Apokolite, he's marked for the New Gods cull currently underway. Possibly Little Barda too. I have no idea where she comes from, but the name suggests a New Gods connection. So it may be the whole thing was simply a hit on Power Boy and everyone else got caught in the crossfire.
Either way, doing a story featuring the shock death of Power Boy is pretty limp. I mean, what's the shock? Power Boy killed by a different mysterious psychopath from the one you were expecting? And while I don't know there was anyone who cared enough to want him dead, I suspect he will be the least missed. It's not like anyone is going to admit to liking him when his defining characteristic was an unhealthy obsession with Supergirl, as Judd Winnick reminded us of here.
In fact he devoted several pages to a sequence about how funny it was that Power Boy was such a creepy stalker that he gets girls to dress up as the object of his obsession when he has sex with them.
Judd, a word of advice: you'd be more convincing with the "not a misogynist" argument if you didn't write things like this. Also, avoid writing humour; you're crap at it.