Thucy, there is an old Ghandi quote, "an eye for an eye makes the whole world blind"
I personally believe that we are responsible for our actions, in every sense of the word. If you end a life, and feel no (or little) remorse, then I have no problem with execution. The death penalty is a touchy issue, but we need to stand up for what is right. This man is dangerous, and when you end a life, many times you forfeit your own.
That said, my brother is a marine, and I do believe that war and national security is necessary. However, this man does not deserve life. Anyone who defends him, add power to his actions. By letting him live after he killed so many people, it is a precedent of weakness, and lack of will. While it is sometimes correct to be lenient, now is not that time.