Re: WWYCD: think of the children
Man what a tough decision! Every character I have played would be torn on this issue. My characters tend to think four color, so they would want to hunt a MURDERER down, regardless of any "noble" intentions. BUT as a father I doubt any of my characters would do to much in the way of actually trying to stop the killer from from doing his duty... I mean exacting his vengence.
Let's do a little meta thinking for a minute... let's say one of my characters knew that it was actually a close friend of his that doing the killing (unlikely I KNOW), given his mentality he wouldn't agree with or help the killer but he would PROBABLY protect the killer from any metahuman/ supers that would come after the killer (i.e. "If anyone is going to bring him in it's going to be me.") One of my mentalist characters might even go so far as to provide mental shielding for the killer so mentalists couldn't just go *ding* "There he is!"
Are we so sure he's acting alone?
It sounds to me like he either is/was a cop, knows a cop, worked for some kind of law enforcement agency at some point, worked Loss Prevention, or something else to have so much knowledge of police tactics.
The problem with copycats is they most likely wouldn't be a restrained as the killer was (i.e. Bombs, machine gun fire, possibly views people harmed or killed as "acceptable losses). How would the killer handle a copycat like that?