Mass shootings in U.S. history

POSTED: 07:20 AM PDT Jul 20, 2012    UPDATED: 05:39 AM PDT Apr 03, 2014 
Fort Hood

A gunman opened fire at the Fort Hood military post in Texas on Wednesday, killing three people and wounding 16 before committing suicide. Take a look at some of the worst mass shootings in U.S. history.