There is the expression, "See Something - Say Something".

The Chattanooga shooter supposedly had depression but still had guns and went to shooting ranges. No one said anything.

He got the guns from somewhere yet undisclosed. His parents didn't know their depressed son had guns?

He wrote a cryptic text to a friend and the friend doesn't question it?

I applaud the Boston cop who turned in his son for terrorist plotting.

It would be a very difficult task but would you call the FBI on your child if you had a very strong suspicion they might be plotting terrirism?

The general attitude in America with the letigious actions at the slight drop of a hat, along with the fear of hurting someone's feelings along the way or even the possibility of being wrong.....altogether dampen enthusiasm for see something say something to work.

There is a fear that those intending to do right by saying something will some how be turned into victims; regardless the good intention or potential saving of lives.

I know full well if I received Facebook messages from anyone that said they were planning to kill someone else, I would let authorities know about it.

Me too.
I do not use social networks. I much more prefer the more up close and personal, real view of the world around me.