I’m a criminologist with a bit of understanding of crime scene investigation, as well as what makes shooters tick. But, really, you don’t need to have these qualifications to put together a reasonably accurate account of the Sandy Hook massacre. You just need to listen to what the police, the medical examiner’s office, and other authorities are telling reporters. A knowledge of firearms helps, of course.

Adam Lanza pictured in a photograph from 2005 in Newtown, Connecticut
One of the ironies of this event is that right wingers would rather trust hasty reporting by the liberal media in the immediate aftermath of the shooting, in particular the December 15 Today show coverage (in which numerous claims were made that turned out to be completely wrong), than believe the experts and authorities investigating the event.
Sandy Hook is not part of a conspiracy to disarm the populace. Here’s what really happened: A troubled young man living in a climate of gun enthusiasm in a dysfunctional house full of high powered and assorted weaponry went to an elementary school with four of those weapons, took three inside with him, and proceeded to murder 26 children, teachers, and administrators.
The guns used in this crime were legally purchased. His mother taught him how to use a firearm and took him to the firing range to practice. He was trained and willing to kill.
The only way this particular tragedy could possibly have been prevented is if any household with the presence of one or more diagnosed mentally ill persons were barred from owning firearms (which, if you know anything about the prevalence of mental illness would disarm a lot of households).