Taliban applauds Boston attack but denies involvement

American law enforcement officials don't know who carried out the attack that killed at least three people at the Boston Marathon, President Obama said at a press conference Tuesday.

“This was a heinous and cowardly act, and given what we now know took place, the FBI is investigating it as an act of terrorism,” Obama said in remarks from the White House press room. “Any time bombs are used, it is a terrorist act.

"What we don't yet know, however, is who carried out this attack or why, whether it was planned and executed by a terrorist organization, foreign or domestic, or was the act of a malevolent individual."