America grapples with questions about public safety after attack at Boston marathon

The United States awoke Tuesday to grimly familiar scenes of bloody mayhem as the nation responded to yet another apparent terrorist attack on domestic soil — this one at the Boston Marathon — and wondered who heartlessly targeted civilians 12 years after Sept. 11, 2001.

Three people were killed and almost 150 injured at the finish line of the Boston Marathon, some with devastating injuries, after two bombs went off 16 seconds apart as the most celebrated race of its kind in the country was winding down.

One of the victims was an eight-year-old boy running in memory of the 20 first graders massacred in December in a mass shooting in Newtown, Connecticut.

Federal investigators were searching for those responsible as Americans were once again left reeling from scenes of blood-soaked chaos while grappling with questions about public safety.

Both bombs, packed with ball bearings, were apparently placed in garbage bins at the finish line of the marathon on what’s known at Patriot’s Day in Massachusetts.

By most accounts, they were small, crudely manufactured devices that nonetheless had devastasting impact — several of the wounded had their limbs blown off in the blasts, including at least one marathon runner who lost both legs.

U.S. President Barack Obama urged calm.

“People shouldn’t jump to conclusions before we have all the facts,” he said on Monday. “But make no mistake, we will get to the bottom of this, and we will find out who did this.”

Bill Keating, a Massachusetts congressman who’s a member of the House of Representatives’ homeland security committee, called the bombings a “sophisticated, co-ordinated, planned attack.”

Law enforcement authorities, including bomb experts, searched an apartment in Revere, Mass., a Boston bedroom community northeast of the city, and reportedly removed some items from the home. They were saying little publicly, however, about how the search was linked to the bombings except to acknowledge it involved a “person of interest.”

Investigators were also poring over the bombing sites in downtown Boston for clues. They hope that two unexploded devices recovered soon after the devastation could yield fingerprints and provide crucial information on how the bombs were designed.

The FBI was said to be closely examining surveillance camera images and was expected to issue subpoenas for records from cell towers in the area.

The bureau’s Boston division urged people to be in touch with any information, photographs, videos or details from the bombings.

“No piece of information or detail is too small,” it said in a statement.