President Barack Obama pronounced the deadly Boston Marathon explosions an act of terrorism on Tuesday as individuals close to the investigation said the two bombs were made of pressure cookers packed with ball bearings and metal shards that cut into the victims.
Speaking at the White House, Obama said investigators do not know if the attack was carried out by an international or domestic organization, or perhaps by a "malevolent individual." Three people were killed, including an 8 year-old boy, and more than 170 were wounded.
In his second public statement in less than 24 hours since the explosions, the president said, "Clearly we are at the beginning of our investigation." He urged anyone with information relating to the events to contact authorities.
Individuals briefed on the probe said the two bombs were made up of pressure cookers, one packed with ball bearings and the other with shards of metal, presumably to inflict maximum injuries. The bombs were placed inside black duffel bags on the ground near the finish line of the annual race, they said, speaking on condition of anonymity because the investigation remains active and they were not authorized to be quoted by name.