Lessons to be learned:
Mindset outweighs Hardware
Spare ammo is a good thing!
Caliber does not win gunfights
Even good hits don't stop people, it may take a lot of "Good Hits"
Train for the worse, pray for the best.
The difference between police officers and the citizenry is police officers intentionally place themselves in harm's way, that I understand, but do you understand a guy like this, may be the one attacking you?
H/T to Uncle