President Barack Obama makes a statement to the press following the explosions near the finish line of the Boston Marathon in the Briefing Room of the White House in Washington

President Barack Obama makes a statement to the press following the explosions near the finish line of the Boston Marathon in the Briefing Room of the White House in Washington

*President Barack Obama just wrapped up his second briefing on the Boston bombings, calling them a “heinous and cowardly act” that the FBI is investigating as an act of terrorism.

“Any time bombs are used to target civilians, it is an act of terrorism,” Obama said, adding that it remained unclear who carried out the attack and why.

Obama said that “this is a good time for all of us to remember that we all have a part to play in alerting authorities if you see something suspicious,” telling Americans to “speak up.”

The president had held off using the term “terrorism” in brief remarks Monday. Today, he spoke after being briefed by FBI Director Robert Mueller, as well as Attorney General Eric Holder, Homeland Security Secretary Janet Napolitano, and White House counter-terrorism adviser Lisa Monaco.

The bombing has killed at least three people and injured more than 170 others.

Shortly before his remarks, Obama ordered flags at the White House and other government buildings be flown at half-staff in honor of the victims of Monday’s attack.

The flag lowering is “a mark of respect for the victims of the senseless acts of violence perpetrated on April 15, 2013,” Obama said in a proclamation.