Re-read what you wrote. Do you think he schemed and worked out some plan to "get away with it"? Of course not.
These conflicts happen because people are territorial. Government exists in part to work out ahead of time just who gets control over what territory and to establish a system for dealing with trespass.
Problems arise when government decides to ignore this basic responsibility and instead focus on more fun things like giving money away.
Now the shooter here obviously should not have done what he did. His instincts took over. He returned to a state of nature. But that's what happens when government stops working -- you end up with a Chicago or a Detroit moment on the banks of the Meramec.
This would never have happened in states that were very restrictive on gun ownership, or that didn't allow citizens to defend themselves. In Britain, for example, it would never happen because people aren't allowed to own guns or use them against burglars. In New York and Chicago, it would not happen because law-abiding citizens are afraid to use the few guns they are allowed because someone is on their lawn. But in liberty-minded states, people are accustomed to defending their property and themselves with their own guns, and calling the cops as backup.
When idiots use guns to do something because they think they are legally allowed to take a life, and they are wrong about that, it hurts those of us who believe strongly in the properly applied principles of self-defense. There are good people in Missouri, women mostly, who will be swayed now to demand more restrictions on guns or self defense laws. That would be wrong. What is needed is better education of those who own guns on when you can and can't use them. I don't know how we do that, or if I think we should require some basic knowledge with ownership of a gun. I don't want government involved in "granting" us our God-given rights. So how do we engender responsible ownership by knowledgable people? This guy, the shooter, clearly had no idea what he was doing, and thought that people on his property were fair game.
Who's "he"? The shooter?
What makes you think I was talking about the shooter?