In our Concealed Carry License Class, we discuss in great detail the use of deadly force. Specifically, we talk about instances when a person legally carrying a firearm can and cannot use deadly force. Yes, there are some grey areas; when the use of deadly force is a judgment call.
There are, however, instances when deadly force should NOT be used. When a threat of great bodily harm or death is no longer in place, you most certainly need to maintain a state of readiness. You may need to call 911. You may want to take the opportunity to remove yourself from the area. It depends on the situation.
The following links are to stories where an individual used deadly force in instances where, in my opinion, such force should not have been used.
Compare these instances with the shooting at the Clackamas Town Center outside of Portland, OR. Here we have another instance of when NOT to shoot, and good judgement.
Remember the four rules of gun safety, and when you can and cannot use deadly force. Review this information regularly.