Bombs kill three people, wound more than 100 at Boston Marathon

Two bombs ripped through the crowd at the finish line of the Boston Marathon on Monday, killing three people, causing several amputations and injuring more than 100 in what a White House official said would be handled as an "act of terror." It was the worst bombing on U.S. soil since security was tightened after the attacks of September 11, 2001, and President Barack Obama promised to hunt down whoever was responsible for the attack on a day when tens of thousands of spectators packed the streets to watch the world-famous race.