One of you will end up here next!
I would always prefer an AR15 when going into a possible shooting. Unfortunately most police are stuck with a 9 mil pistol when all hell breaks out. In most shootings the hit ratio drops to 1 in 3 shots if you are lucky. It is not uncommon for a police officer to empty his pistol without a single hit. Unfortunately it is human nature to try and get off that first shot and then once the firing starts panic and adrenaline take over and 5 seconds later you are shooting an empty gun with no hits. Then the panic loading and shooting really gets under way. The problem is most officers or Joe public get in one fire fight in their life if their luck runs out. Fortunately most people never get in one.
Very few people practice making that quick move to cover then a relaxed methodical shot that ends the fire fight in 2 seconds.
Numerous studies also show that depressed people tend to become more suicidal the longer they are on SSRIs, and it becomes easier to carry out. I would say kamikaze massacres where you feel you have nothing to lose falls under that category.