These dreams are often (so I'm told) had by cops. I had a similar dream, being a cop, that my partner and best friend was held hostage with a shotgun to his head. It took some time for me to get a clear shot and neutralize the threat... much more time that would be practically possible in a real situation.
I've heard it explained dreams such as this reflect on one's hesitancy to pull the trigger and end a human being's life. A "click" may mean you aren't ready to do so... could be psycobable BS too...
I dream things going "bad" at work a lot, often times based on what I have recently experienced. One re-occurring dream was that of a 11yo boy whom was shot repeatedly and I was unable to save him lasted for several months.
At the end of the day, I think these dreams enbable us to process/prepare for traumatic sitations.