Take a look at some of the worst mass shootings in U.S. history.
Sources say close to 30 people were killed, many of whom were children, during a school shooting the Sandy Hook Elementary School in Newton, Conn.
CNN Exclusive/Richard Dessin
Boy Scouts of America
Library of Congress
Karen Barefoot/SXC
Lucas Jackson/Reuters
Pool
Kevin Taverner/CNN
Auction Team Breker
Chuck Kennedy/The White House
istock
Fred Prouser/Reuters
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