Been thinking and prob shouldn't

   So I had this thought, one I probably shouldn't, but I did. Nothing dirty or sexual or anything.
   See I was thinking about death and what it means to people.
   If a person came up and shot your mom in the head, without thinking. Then someone came and killed that someone. Whos life and whos death was worth more?
   I mean was the death of your mother worse than that of the killer? Was there more to her life than that someone who killed her? Can we choose one life over anothers because of a single action? Can we judge a person at all?
   Can we say that the death of your mom was horrible and nothing good came of it? But turn to the shooter and say their death was a great benifit to the human race and society? If that someon had died before they shot your mom and she died anyway would that be different?
   Is there a reason why one death would be called good while the other is tragic? Would not both deaths be a sad event? Can there be a sense that one life is better than anothers?
Is the killing of one person better than the killing of another?