Lethal force can’t be used by an individual to protect property - just for self defense. Even then you have to be in fear for your life or the life of others.
LEOs get more leeway, but even then, the better be in fear for their life - look at Officer Wilson.
“Lethal force cant be used by an individual to protect property”
which is bogus and needs to change
So, they could only shoot if their lives were threatened.
If I'm standing on a rooftop and some miscreant has a molotov cocktail, do I have to wait until the building under me is in flames or can I drop them and let them stew in their own juices?
Depends on the state