There's also a huge difference between screaming the latter to unrelated people and screaming it to the so-and-so neighbor.

Not exactly. He didn't say he "could" shoot up a kindergarten, he said he was going to. Is there a difference between naming a specific kindergarten? Absolutely. But that doesn't mean only one of them is a threat.

In my example, both use the 'could.'

I really don't think that someone should be charged with 'making terroristic threats' - nor any kind of threats - with just a vague statement of intent.