Marcus Weaver spent three years talking openly about forgiving the man who shot him. He didn't want to see James Holmes executed.

But by the time Holmes was convicted in the chilling 2012 attack on a Colorado movie theater, Weaver had changed his mind.

Now, Weaver says, the death penalty is the only just punishment for the mentally ill former neuroscience student who murdered 12 people and tried to kill 70 more.

The jury is set to begin deciding whether the 27-year-old Holmes should be sentenced to life in prison or death by injection. But Weaver's transition shows there are no easy answers, not even for those who most want to see Holmes punished.