When something like this happens, it is tragic, for the people who cared about the person that died. It's not tragic for the dead guy, who is well out of harm's way (though a shot from a 44 would probably hurt, for a minute). But for, say, his friends, his mom, etc., it is sad.
We had a case down here a year or two back, where a mentally retarded man went and found himself a handgun, and found some police officers, and pointed the gun at them, and said he was going to kill them. This is a grown man with the mind of a four year old, more or less. They killed him, shot him 8 times in the chest, I believe. There was really nothing else they could do, except maybe wait and see if he shot them. They took the only sensible course of action, and committed no wrongdoing. It was still really sad for the man's family, though, who lost their son, whom they viewed as harmless. Of course, the burden of guilt was on them, really, since they left him alone, and let him get hold of a gun. it's tragic BECAUSE there was no alternative to the action taken.
In this case with Herrera, it sounds like he was not of sound mind after he chose to drink. Some people are like that, for whatever reason. They shouldn't drink. But once he did, he was what you might call "out of control", in other words, not of sound mind. The homeowner did the right thing, he made a sensible choice and may very well have saved his own life or someone else's. But it's still sad that this is what happened, instead of justin herrera choosing to stay sober and in control, and then getting to have a nice breakfast the next morning.