The sound of the explosion and getting covered with paint could have givien the old guy a heart attack
A nice big sign saying PRIVATE PROPERTY would have been good.
If he was warned, he deserves it -BUT- imagine if the old guy had croaked... the owner might be facing manslaughter charges. Would you want to risk that?
Where I am from, nobody cares about your signs
They will walk right past them
and give you the finger
I call the cops, let them deal with it, and they usually do a good job. I have successfully won money awards from trespassers. I used the money to build a concrete wall. Strange walls do work and I got the trespassers to pay for it....
That posting may have been inadequate. In many states, the exact wordage in the statute must be used, for example, “POSTED-No TRESPASSING”. :-)