The nation has experienced its share of tragedy this week. The Boston Marathon bombings that killed three people and injured scores. A scare from suspicious letters that reminded people of the anthrax poisonings shortly after 9/11. And last night a fire and massive explosion at a fertilizer plant in the town of West, Texas. More than a dozen people are believed to have died and 160 injured. Authorities are treating the plant as a crime scene until more is known. No connection has been found among the explosions in Boston and Texas and the suspicious letters. Diane and her guests discuss the latest on the tragedies and investigations.