There's a difference between a guy who went through a body scanner and a fleet of sniffer dogs and a guy who sends a package that goes through essentially no security (though you would think these guys would employ better security simply as they are higher profile people who get lots of threats).
And I'm not saying that threats shouldn't be investigated, or even that exercising your freedom of speech doesn't have consequences (it does and should).
But after they looked into his home life. Spoke to his friends. Tossed his room and spoke with teachers. And still found no actual evidence of a plan to commit a crime. The next step is get into contact with Facebook and get that thread. It wouldn't be hard and I'd assume FB gets this sort of request all the time. They probably have a protocol in place.
I'm saying that just saying that you're going to commit a crime is not the same as doing it. And that an idiot kid who says something on Facebook is not and should not be considered, the same as a billionaire-backed, militarily trained terrorist.
Do some disturbed people make threats on Facebook and then carry them out? Yes they do. And so yes, these things should be investigated thoroughly. But the case here was not investigated, it was rushed and sloppy.
Did the police go get the thread themselves? No.
Did the police get the kid a psych eval? Not that I've seen here anyway.
Did the police do any real investigation? No.
Innocent until proven guilty. That's the way it's supposed to be.