Live updates: Krystle M. Campbell mourned as 2nd Boston bombing victim

Friends of 29-year-old Krystle M. Campbell mourned her Tuesday as the second victim of the Boston Marathon bombings. On Facebook, employees of the Summer Shack restaurant in Hingham, Mass., where she was general manager said they were devastated “by the loss of our beloved Krystle.”

“She was an incredible woman, always full of energy and hard at work, but never too tired to share her love and a smile with everyone. She was an inspiration to all of us,” Summer Shack employees wrote.

PHOTOS: Bombings splashed across nation’s front pages

Campbell’s father, William, who could not be reached for comment, told Yahoo News that he was in shock. She had been at the finish line with a friend cheering on her boyfriend, who was competing in the race.

Foreign or U.S. terrorists? Crude bombs show ‘some skills’ | 11:48 a.m.

Investigators gathering forensic evidence about the explosion that tore through the finish-line area of the Boston Marathon are looking at the type of improvised explosive devices that were used in the terror attack, seeking clues that officials hope will lead them to suspects.

The device is considered to be crude, leading some federal investigators to hypothesize that they were domestic rather than international in origin, according to three federal law enforcement officials. But while unsophisticated, the devices did show signs of having been constructed by someone with at least some experience in explosives, officials said.

VIDEO: Boston marathon explosion

Two bombs exploded on Monday, killing at least three people and injuring 176 others in what officials on Tuesday termed a terror attack. But it is unknown if the perpetrators were foreign or domestically-inspired and the type of device could be an important clue.

“It’s somebody with some basic rudimentary skills in circuitry,” said one official. “So there’s a level of experience here. And that shows some skills.”

Federal law enforcement officials said that initial signs suggest the devices were explosives that fit into backpacks, and that the assailant or assailants triggered the explosions by using timing mechanisms or set them off remotely using a cellphone.

Doctors remove pellets, nails from bombing victims | 10:03 a.m.

Authorities pressed their investigation into who was responsible for the terror bombing at the finish line of the Boston Marathon as doctors on Tuesday supplied new evidence that the wounded had been maimed by material including metal pellets.

Dr. Ron Walls, chairman of emergency medicine at the Brigham and Women’s Hospital, said Tuesday that three of the patients treated at the hospital had shrapnel that appeared to include objects he described as small, round metallic pellets about two to three millimeters in diameter, similar to BBs. He said doctors also removed about a dozen small carpenter nails from one of the patients.

Boston officials said three people died and 176 were injured in the two explosions at the end of Monday’s marathon. President Obama on Tuesday said the explosions were being investigated as an act of terrorism.

Officials have said 17 of the wounded were listed in critical condition.

Brigham and Women’s treated 31 patients, of whom 16 have been discharged. Walls said nine have been operated on and five remain in critical condition. One patient had a below-the-knee amputation and two others are still at risk of losing limbs, he said.

Dr. Mike Zinner, the head of surgery, said one patient suffered “very significant” head injuries. Zinner also said there was a patient with a penetrating neck injury, although the patient was operated on successfully. He said the trauma surgeons would likely not remove all the shrapnel from patients.

Obama labels marathon bombings a terrorist act | 8:56 a.m.

President Obama said the bombing at the Boston Marathon was being investigated as an act of terrorism and insisted that the country will not bow to such violence.

Speaking about the tragedy for the second time in as many days, Obama said the nation’s prayers go out to Boston. The two explosions on Monday killed three, including an 8-year-old boy, and wounded an estimated 176 people, Boston officials said earlier.

“This was a heinous and cowardly act and given what we now know about what took place, the FBI is investigating it as an act of terrorism,” Obama said in televised comments from the White House. “Any time bombs are used to target innocent civilians, it is an act of terror.”

“What we don’t yet know, however, is who carried out this attack or why,” the president said, pledging to use all resources to find those responsible. ”We will find whoever harmed our citizens and we will bring them to justice,” he insisted.

“We also know this,” Obama said. “The American people refuse to be terrorized.”

Jittery Boston seeks clues to bombing that killed 3 | 8:05 a.m.

BOSTON -- This jittery city awoke Tuesday to heightened security after two bomb blasts shattered the finish of its famed marathon, killed at least three people, wounded scores more and left everyone wondering who was behind the latest act of terror to cast a pall on the nation.

More than 400 members of the National Guard patrolled downtown, securing the scene. The adjacent blocks around famed Copley Square were blocked off with metal barricades and police tape, and many streets were shut down to most traffic. Police and uniformed soldiers were allowing guests at nearby hotels -- some still in marathon gear -- to enter the restricted zone to retrieve their belongings from their rooms. Canine units were in the area.

“Everyone should expect continued heightened police presence, and everyone should continue personally to be vigilant,” Massachusetts Gov. Deval Patrick said at a televised news conference with top officials Tuesday. “The investigation continues and until it is done all of those in law enforcement represented by the leaders here will be present in force in the area around the blast and throughout the city.”

Patrick said no unexploded bombs were found at the Boston Marathon, contradicting earlier reports. Only the two bombs that exploded were found, he said.

“Yesterday, this terrorist brought to the city of Boston, tragedy,” Mayor Thomas Menino said and went on to praise first responders.

An 8-year-old child was among the dead, and his mother and sister were among the about 176 people who were injured when the explosions went off, within seconds of each other and less than 100 yards apart. At least 17 were listed in critical condition, officials said on Tuesday and were being treated at nine area hospitals.

The blasts were near the finish line of the Boston Marathon, the traditional 26.2-mile race that is a feature of the festivities surrounding Patriots Day, a state holiday that commemorates the first battles of the American Revolution. Runners were hurled to the ground, windows were shattered in the heart of an area rich with famed buildings. Plumes of smoke rose over spectators as Boylston Street was turned into a zone of chaos.

“This was a very powerful blast. There were serious, serious injuries,” said Boston Police Commissioner Edward Davis. “This cowardly act will not be taken in stride. We will turn every rock over to find the people who are responsible for this.”

The Boston patrols were a show of force that was mirrored in cities from Los Angeles to New York, including the nation’s capital, as security was increased around the country. Police eyed commuters in subways, cordons of security around landmarks were extended and everyone was urged to report suspicious packages and people.

Officials, led by President Obama, vowed to leave no stone unturned in the search for responsibility and pledged that justice would be swift.

But it remained unclear at whom the nation would direct its vengeance. Officials privately were calling the bombings an act of terrorism, but whether it was international or domestically inspired was still unknown.

In Washington, a U.S. government official said Tuesday that there had been no intelligence about a possible attack in Boston during the weeks leading up to the bombings -- a position that officials have maintained since the blast.

“I received two top secret briefings last week on the current threat levels in the United States, and there was no evidence of this at all,” Rep. Peter King (R-Long Island) said on MSNBC’s “Morning Joe.” Until this year, King was chair of the House Homeland Security Committee and is now on the Intelligence Committee.

There was “no intelligence that seemed to be out there. Now people will look back and see if something was missed. I don’t know if there was or not,” he said. “This should be a wake-up call to everyone, that the war against terrorism is far from over.”

The FBI is the lead agency on the investigation of the blasts. There have been no claims of responsibility, but at least one foreign group, the Pakistani Taliban, which has threatened attacks in the United States because of Washington’s support for the Pakistani government, on Tuesday denied any role in the bombings.

The FBI did serve a warrant late Monday and searched an apartment in the Boston suburb of Revere. Some investigators were seen leaving the house early Tuesday carrying brown paper bags, plastic trash bags and a duffel bag.

Officials have described the explosives as relatively simple and not the kind of plastic explosive material normally associated with foreign terrorists.

At the Tuesday news conference, FBI Special Agent in Charge Richard DesLauriers said officials are following a number of leads, but he gave no details. There is no known physical threat at this point, said officials. ATF agent Gene Marquez said authorities are seeking amateur video and photographs to help their probe.

DesLauriers would not discuss whether any suspects were in custody, but acknowledged that authorities were interviewing people.

The explosions were timed for maximum damage coming about four hours into the race when the majority of recreational runners were expected to cross the finish line. Elite runners completing the famed course had finished at just after the two-hour mark but by the time the explosion went off there were still thousands of runners puffing their way to the end.

The number of wounded has continued to increase over the hours.

“This is something I’ve never seen in my 25 years here,” Alasdair Conn, chief of emergency services at Massachusetts General Hospital said. “This amount of carnage in the civilian population. This is what we expect from war.”

Other doctors said they have recovered pieces of metal from the wounded but it was unknown if that was just debris from the explosion or part of the weapon.

One of the dead was identified as Martin Richard, 8, whom neighbors in his Ashmont area described as a boy who loved to ride his bike and play with his older brother Henry and younger sister Jane. Richard reportedly was at the marathon to watch his father, Bill Richard, run, and was at the finish line with his mother and two siblings.

“Losing one child is bad enough, having the other ones injured and your wife injured,” next-door neighbor Jane Sherman, 64, said, trailing off. “They are a wonderful family and this is a horrific tragedy. I think this is something they won’t recover from.”

Officials at the news conference said the city will recover from the tragedy, but the scars were still fresh. Inside a downtown-bound Red Line commuter train, riders were quieter than usual.

“Everyone’s down,” said Leo Doolin, 49, of Dorchester, who was reading a newspaper article about the explosions. “Everybody’s very quiet.”

Deanna Lewis, 21, a junior at Boston University, said people would just try to get on with their routines.

“We’re just trying to continue on with our daily lives,” she said as she studied a notebook while waiting for her train. “Everyone has to go back to work or school.”

But she added: “There is still fear.”

At a briefing Tuesday morning, law enforcement officers asked anyone who took pictures or video of the finish line at the time of the blast to email them to boston@ic.fbi.gov or to call (800) 225-5324.

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Bengali reported from Boston and Muskal from Los Angeles. Times staff writers Alana Semuels and Andrew Tangel in Boston and Brian Bennett, Richard A. Serrano and Michael A. Memoli in Washington contributed to this report.