I wonder how the families of the three killed would delineate between "Shooting" and "Massacre".
What delineates it in your mind? If one of the other 7 had died, would that stop being a shooting and become a massacre? 3? Does it have to be 10+?
Please proceed.
Not sure why you are so concerned about semantics, but I'll play along. I'll say a massacre is if more people are killed than you can carry comfortably in your average American made mid sized sedan.
That a good enough answer for you, or shall I proceed further?