I dont think the teacher went over the line.
The reason why he had the 10 mm was to protect himself from wild animals. 10 mm pistols are usually used for pistol hunting and that was a good choice of weapon from protecting you against animals. There are some big animals out there like bears , dogs and mountain lions.
In any situation, you have to ask yourself what could have been done better. In this situation, the teacher could have retreated more away from the situation. He instead chose to stand his ground. For example, the dogs were coming at him and he drew his weapon, fired a few warning shots then he should have backed away. Not just backed away, but kept putting distance between the dogs, the owner and himself. He could have also shouted threats and fired additional warning shots at the attacker. Maybe even put a round into the attackers legs to stop the advance. The attacker wasnt armed and just needed to be disabled.
The attacker should not have charged a man with a drawn pistol. Whenever you are up against a man with a drawn pistol, whoever they maybe, then you do not want to advance towards them. Again, you want to move slowly and try to distance yourself from them with your hands in the air. The worst thing you can do is charge the man with a gun or shout hostile words at him.
I believe there were things that could have been done better, but it was a clear case of self defense. The dogs attacked the teacher, the man charged at the teacher shouting words and the teacher had to protect himself.
If you have a drawn pistol and someone is charging at you, then it can be reasonably assumed that the attacker is going to disarm you and then use your weapon against you.
As the below video demonstrates, its possible for someone to take that weapon away from you and use it against you.
However, at the end of the day, the best advice is to do whatever you can to avoid these situations. Never make attempts to stand your ground. Put distance in between yourself and strangers.
Understand that if you fire your pistol then you will be in court.
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Quote from Kicking:
Except if you live in some parts of the US that still have Wild West laws the best thing you can do I would say is to just stay out of trouble, avoid any fight or use of a weapon.
I know that when you have weapons you tend consciously or not to WANT to use them, you sort of dream up all kinds of scenarios where you may have to use it. The fact is it's very unlikely you will ever have to use your weapon if you are not a LEO. So I think by all means know how to use it but maybe not to the point where it becomes a second nature and you shoot as a reflex.
This teacher who shot 3 rounds in a (I understand unarmed) individual went over the line. The guy sounds like a nut, shooting warning shots for 2 dogs running at him ! Unfortunately that's what may happen when you carry a handgun and are paranoid
beyond reason.
In the end the police and the govt are as much your enemy as the "bad guy". And the bad guy, if you knew where he comes from maybe you would understand , some people though are so evil you don't want to give them any chance.
Best way to avoid trouble is to keep a low profile, avoid being a target to start with. If you get into trouble with the cops, don't trust them, stay polite and keep your mouth shut. We law abiding citizens tend to trust the police but we really shoudn't .
Now I know all that is easier said than done.