Understanding the Brains of Mass Killers
![](https://media.wnyc.org/i/800/0/c/85/photologue/images/23/newtown_ct_pray_sign.jpg)
Sign in Newtown, Conn., after the mass shooting in December at Sandy Hook Elementary School.
( Ilya Marritz )
( Ilya Marritz )
Produced by Arwa Gunja