Congress reacts to Boston Marathon bombings

WASHINGTON -- Congressional leaders reflected with grief on the tragic loss of life in the bombings at the Boston Marathon on Monday, but had few immediate answers as to the nature of the attack.

The flag over the U.S. Capitol was at half staff and there were signs of increased security on the grounds Tuesday.

House Speaker John A. Boehner said words can’t express the “sorrow” lawmakers feel for the families that lost loved ones and for those who were wounded. The attack was a reminder “of just how vulnerable” we are, he said, “in this era of what I’ll call modern warfare.”

“We don’t know who perpetrated this or for what reasons, but I’m confident that we’ll get to the bottom of it,” he said at a news conference. “It’s a terrible day for all Americans, but we carry on in the American spirit. We will come together with grace and with strength.”

FULL COVERAGE: Boston Marathon attack

The U.S. Senate opened as usual with a prayer from Chaplain Barry Black, who said the bombings “remind us that we live in a dangerous world and that human life, regardless of the level of physical excellence, is fragile.”

Senate Majority Leader Harry Reid acknowledged that there remain questions about “who did this and why,” but said federal agencies are “investigating this attack as aggressively as possible.”

The Senate Republican leader, Mitch McConnell, said the events ended a “complacency” that had set in, not unlike before the 9/11 attacks, for many in the nation.

“And so we are newly reminded that serious threats to our way of life remain. And today, again, we recommit ourselves to the fight against terrorism at home, and abroad,” he said.

Other key lawmakers had few definitive answers in the immediate aftermath of the attack Monday night. Sen. Dianne Feinstein, who chairs the Intelligence Committee, said she understood it to be a terrorist incident, but did not know whether it was foreign or domestic in nature.

There was “no intelligence, to the best of my knowledge, that would point out that there was an attack on the way,” she added.

VIDEO: Boston Marathon explosion

“The use of improvised explosive devices, the presence of more than one device, and the horrible carnage and death and injuries all suggest that this was a carefully planned event,” said Sen. Susan Collins (R-Maine), a member of the Intelligence Committee who until this year was the top Republican on the Senate Homeland Security and Government Affairs Committee.

“I think this is another reminder that the fight against terrorism continues and that we cannot be complacent and let up on our efforts.”

Rep. Peter King (R-N.Y.), a member of the House Intelligence Committee, said on MSNBC that he had two classified briefings in the past week, and “there was no evidence of this at all, no intelligence that seemed to be out there.”

“Now people will look back and see if something was missed.”

Massachusetts Sen. Elizabeth Warren (D-Mass.) had not yet left her state when the attacks occurred, and canceled travel plans to return to Washington for a Monday evening vote. Mo Cowan, recently appointed to fill the seat held by John F. Kerry, reflected on the significance of an attack on Patriots’ Day.

PHOTOS: Explosions at Boston Marathon

“It’s a rich day, celebrating the first battles of the American Revolution,” he said. “[Monday] was a great day of celebration until this horrific tragedy occurred. But the people of Boston are strong, they are resilient.”

Democrat Chris Murphy of Connecticut, the Senate’s youngest member, had just run a 10-mile Cherry Blossom race in Washington a week ago.

“People just went up there to enjoy a beautiful day and it ends in tragedy,” he said.

Follow Politics Now on Twitter and Facebook

Michael.memoli@latimes.com

Twitter: @mikememoli