Investigators believe Boston bombs were pressure cookers hidden in backpacks, officials say

Boston Police Department Commissioner Ed Davis urged spectators at the Boston Marathon to send images and video around the time of the blast that may give them clues on the deadly bombings. Link: http://usnews.nbcnews.com/_news/2013/04/15/17767721-investigators-believe-boston-bombs-were-pressure-cookers-hidden-in-backpacks-officials-say?lite