Obama orders flags lowered after Boston explosions

President Obama has ordered flags at the White House and all government buildings to be flown at half-staff in honor of the Boston Marathon explosion victims.

Obama signed a proclamation making the order Tuesday morning, calling it a "mark of respect for the victims of the senseless acts of violence" perpetrated in Boston the previous day. He ordered flags to remain lowered through sunset Saturday.

Three people were killed, including an 8-year-old boy, and more than 170 were wounded in Monday's bombing at the famous marathon's finish line.