Anything from shouting that you’re armed and will fire if they enter. Leaving the home if you’re able too. Warning shot. Visually confirming what you’re killing.
Home invasions are rare especially if you’re not connected to criminal life yourself.
And the kid fucked up. No doubt. Smashing a window, who wouldn’t think home invasion. But having a firearm to defend meant the home owner had time to take other actions and be safe. Actions weren’t taken. Actions that if taken would have prevented this death. Which is why many places don’t have these types of laws. Statistically you’re more likely to make a mistake than encounter a home invasion