I got your FBI document right here (this report actually IS from the FBI)
A Study of Active Shooter Incidents in the United States Between 2000 and 2013
Newtown mentioned on page 7:
>>
INCIDENTS WITH THE HIGHEST CASUALTY COUNTS:
■■ Cinemark Century 16 Theater in Aurora, Colorado:
70 (12 killed, 58 wounded), July 20, 2012.
■■ Virginia Polytechnic Institute and State University in Blacksburg, Virginia:
49 (32 killed, 17 wounded), April 16, 2007.12
■■ Ft. Hood Soldier Readiness Processing Center in Ft. Hood, Texas:
45 (13 killed, 32 wounded), November 5, 2009.
■■ Sandy Hook Elementary School and a residence in Newtown, Connecticut:
29 (27 killed, 2 wounded), December 14, 2012. <<
Again on page 15:
>> Incidents in educational facilities account for some of the higher casualty counts. For example, the highest death tolls among the 160 incidents occurred at Virginia Polytechnic Institute and State University in Blacksburg, Virginia (32 killed, 17 wounded) and Sandy Hook Elementary School in Newtown, Connecticut (26 killed, 2 wounded [1 additional death at a residence]). <<
And specifically listed on page 40:
>> Sandy Hook Elementary School and Residence (Education)
On December 14, 2012, at 9:30 a.m., Adam Lanza, 20, armed with two handguns and a rifle, shot through the secured front door to enter Sandy Hook Elementary School in Newtown, Connecticut. He killed 20 students and six adults, and wounded two adults inside the school. Prior to the shooting, the shooter killed his mother at their home. In total, 27 people were killed; two were wounded. The shooter committed suicide after police arrived. <<