If any good can come out of this tragic situation, it might be that it could serve as a useful reminder that, historically, many countries and civilizations have gone through a cycle where the wealthiest squeeze more and more money out of the economic classes below them.

Typically, the poorest people don't do very much, as they are just trying to survive moment to moment, but the middle classes are better insulated against injustice and have the strength to be more angry about it.

In France, heads rolled.

The suspect for this particular murder went to an Ivy League college and had a white collar job - the very profile of a historical revolutionary.

The celebrated book Capital forewarned that inequality in the US is unsustainable, and it has only got worse since then.

It's not too late for the US, but it must heed these warnings now.