U.S. President Barack Obama has described the deadly bombing at the Boston Marathon as “a heinous and cowardly act.”

Speaking at the White House on Tuesday, Obama said that “any time bombs are used to target innocent civilians it is an act of terror,” adding that the FBI is investigating the bombing.

He said the U.S. has to find out “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."

Obama vowed to the American people that Washington will find whoever harmed U.S. citizens and bring them to justice.