So you can protect yourself by denying the shooter at least one of these. How do you do that?
You can't really, except to stay home. Not feasable. Many people refer to crimes like these as being "random", and it is my belief that very few crimes are "random". The victims are chosen for some reason, (such as in the ACE rule). This is why women are very often victims of crimes..."easy targets"--unarmed, vunerable and seen as being weak. Which is why I encourage all women to minimize risks and get training.
With these MD shootings, as long as the perp(s) have A.C.E. no one is "safe". By the way...A.C.E. is what they teach parents to help them protect their kids from predators. Parents are told to reduce access and cover..in other words....watch your kids and don't let them play in area's where you can't see them and others CAN.