What is the Government to do?

New York Times

Man Charged With Killing Six in Washington State

By DAN FROSCH

Published: September 3, 2008

This news story is about an emotionally unstable man killing 6 people including a sheriff's deputy and hurting 4 more people.  The thing that got me thinking here was, how is the government supposed to deal with this kind of situation?  During class we had to discuss the whole social contract concept that describes a persons natural rights of life, liberty, and property, and how the government is put into place by the people to protect it.  My said question really comes into play with this whole social contract in the way that the government doesn't really have very many options in this situation.  They can't really do anything before hand other than taking every single person in the United States and judging them all for emotional or mental health, but this idea has way too many problems with it, such as the cost it would take, the margin of errors or even just the ethical issues it could bring up.  The easiest option (the method that is in place now) would be to wait and find out who the next emotionally unstable person is, but then an innocent life is long gone and their "social contract" has been defiled.

How should the Government handle situations like this?