Look deeper. My theory:

Adam Lanza and his mother was assassinated. His brother Ryan and the father was supposed to be as well. But things did not totally go as planned that day. Ryan was at work, and got right on facebook and twitter when the news broke about Adam. The father was in an unexpected and unplanned meeting.

Adam did not kill his mother, or the children.

The question here is, what did Adam's father know? What did he see?

The mother kept guns for protection, not the end of the world.

The entire school was a coverup to get rid of Adam and promote the agenda against guns. Never let a crisis go to waste.