First of all, killing someone who has murdered someone is not wrong and shouldn't be punishable...
but my opinion is that it IS wrong for just the average Joe to take capital punishment into their own hands... the government have the responsibility of punishing the murder by death... problem is, they don't.
Eddie didn't kill anyone at that point, so my opinion is he shouldn't have been killed... BUT since it was an accident, I don't see how Peter could be blamed for manslaughter, seeing as Brock jumped in the way... but, of course, in situations like this, the cops (if they heard of the situation) would have the right to arrest him and trial him honostly ONLY if they didn't have the full story. Court's are for getting the full story (not bribing your way out of jail

)
so, if I was a cop, I'd probobly arrest Peter... but if I would have been a witness and saw that it was Eddie that jumped in the way, then I wouldn't.
That's just my opinion and I know capital punishment is a VERY contriversial subject these days, but seriously. If someone takes another's life, then they should be guilty and have their life taken. If our government would do that, this world would be much safer... example... if you planned on killing someone, would you be willing to do it if you knew you'd be killed for it? most wouldn't, for fear... (except the occasional physco)... but... as Peter said "We always have a choice."
That's whats wrong with our government today is that they think that, for example, if you have something stolen from you, then the theif must pay the government back, not the victim. This makes the government rich, and we get less than what we started out with! If the government would punish theives by making them pay the victim 4 to 7 times as much as they stole, I doubt there would be as many thieves!
If the government would use these methods, then I'd almost guarentee 100% that we'd have a more peacefull ciziety.