The Shortest Twenty Minutes in the History of the World

At the police station, dispatchers began to take calls from inside the school. Authorities say the first emergency call about the shooting came in at "approximately" 9:30 a.m.

"Sandy Hook school. Caller is indicating she thinks someone is shooting in the building," a dispatcher told fire and medical personnel, according to 911 tapes.

Police and other first responders arrived on scene about 20 minutes after the first calls.

[link to www.cnn.com]

What happened during those twenty minutes??? Not to mention the first one or two between the time shtf and they called (supposedly).