[quote=@POOHEAD189]
http://www.providr.com/teens-killed-robbing-house/?utm_source=Awwww&utm_medium=facebook&utm_campaign=providr
Three teenagers, ages 18, 17, and 16 respectively broke into someone's home to rob them. After discovering them in the act and 'exchanging words,' the home-owner gunned all three boys down. Thoughts? 
[/quote]

There isn't much detail so it's hard for me to make a definitive statement with so few facts. Ultimately I would say that if 'Zach' had a reasonable fear that his life was in danger at the moment he pulled the trigger than it was a justified killing.