The problem with forgiveness for murderers is that the people who can give it are all dead. For the State or other third parties to “forgive” is an act of moral presumptuousness that implicitly denigrates the victims. The best that the State can do is to deliver retribution in the form of execution. Even better if the victims of prospective murderers fight back and are not murdered in the first place.
I have misgivings about the death penalty in practice because some innocent people are executed. However, none of these concerns apply in the Williams case, since Williams’s guilt was not seriously in doubt. Morally, execution of known murderers is the fairest and least judgmental response and the one that is most respectful of the victims.