we just don't know who is behind it. >> we've been very careful all afternoon to not jump to conclusions. when you see multiple bombings like this, when you hear reporters and witnesses on the scene describing shotgun pellets or bb's, or metal balls that you've seen in these bombings before being used, to really have these explosives have the most mass casualtyies, as you mentioned, the hallmarks of other potential plots. correct? >> correct. i think when you see ball bearings, as you mentioned -- >> here is the president. let me interrupt you. i'm sorry. >> security team on the events in boston. we're continuing to monitor and respond to the situation as it unfolds. i've directed the full resources of the federal government to help state and local authorities protect our people, increase security around the united states as necessary, and