Comment on Boston bombs said to be made from pressure cookers

BOSTON — The two bombs that ripped through the crowds at the Boston Marathon, killing three people and wounding more than 170, were fashioned out of pressure cookers and packed with shards of metal, nails and ball bearings, a person briefed on the investigation said Tuesday.The details on the apparently crude but deadly explosives emerged as investigators appealed to the public for amateur video and photos that might yield clues, and the chief FBI agent in Boston vowed "we will go to the ends of the Earth" to find those responsible.