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“At this time there are no claims of responsibility,” FBI officials said in a press conference Tuesday. “The range of suspects and motives remains wide open.”

Three died and at least 176 were injured when two bombs went off just before 3 p.m., shattering a festive atmosphere several hours after the legendary race began on the city’s 238th annual Patriots’ Day.

Officials found that the bombs consisted of explosives put in ordinary 1.6-gallon pressure cookers, one with shards of metal and ball bearings, the other with nails, a person close to the investigation tells the Associated Press. The bombs were stuffed into black duffel bags and left on the ground, the person said.

Richard DesLauriers, FBI agent in charge in Boston, confirmed at a press conference investigators had found pieces of black nylon from a bag or backpack and fragments of BBs and nails, possibly contained in a pressure cooker. He said the items were sent to the FBI laboratory at Quantico, Va., for analysis. Read more from this story HERE.

Boston Marathon bombs have hallmarks of ‘lone wolf’ devices, experts say

By Tim Lister and Paul Cruickshank. The devices used in the Boston Marathon attack Monday are typical of the “lone wolf:” the solo terrorist who builds a bomb on his own by following a widely available formula.

In this case, the formula seems very similar to one that al Qaeda has recommended to its supporters around the world as both crudely effective and difficult to trace. But it is also a recipe that has been adopted by extreme right-wing individuals in the United States.

The threat of the “lone wolf” alarms the intelligence community. “This is what you worry about the most,” a source with knowledge of the investigation told CNN’s Chief Political Analyst Gloria Borger. “No trail, no intelligence.”

Officials have told CNN that among the materials used in the attack on the marathon were some sort of timing device, a basic mixture of explosives and some sort of metal container containing nails and other projectiles. The FBI said late Tuesday that what appeared to be fragments of ball bearings, or BBs, and nails had been recovered and had possibly been contained in a pressure cooker.

One federal law enforcement source told CNN’s Deborah Feyerick the devices contained “low-velocity improvised explosive mixture — perhaps flash-powder or sugar chlorate mixture likely packed with nails or shrapnel.” Read more from this story HERE.

Boy killed in Boston blast wrote, ‘No more hurting people’

By Ashley Fantz. Almost a year ago, 8-year-old Martin Richard wrote four simple words on a sign at school “No more hurting people,” it said.

For the camera, he held up the bright blue sign decorated with hearts framing the word “Peace.”

It’s a photograph that many find difficult to look at Tuesday as they struggle to comprehend the violence that took Martin’s life. On Monday, the boy and his family were watching the Boston Marathon near the finish line when two bombs exploded just off Copley Square in the heart of the city.

The grade-schooler was killed, authorities said. Martin’s mother, Denise, and his sister were grievously injured, The Boston Globe reported.

Denise Richard underwent surgery for an injury to her brain, and Martin’s 6-year-old sister lost her leg, CNN affiliate WHDH reported. As of 1 p.m. ET Tuesday, both were still hospitalized, according to WHDH. Read more from this story HERE.

Experts have long warned about IEDs in U.S

By Stephanie Gaskell. Military and law enforcement officials have warned for years about the danger of attacks involving improvised explosive devices like the ones said to be involved with Monday’s explosions at the Boston Marathon.

In 2010, the Department of Homeland Security issued a bulletin alerting law enforcement agencies across the country to be on the lookout for pressure cookers, the same kitchen appliance said to have been used to form the two explosive devices that killed three and wounded some 183, many severely.

The cookers, according to the alert, posted online by The Smoking Gun website, have been widely used in Afghanistan, India, Nepal and Pakistan.

“Pressure cookers are common in these countries, and their presence probably would not seem out of place or suspicious to passersby or authorities. Because they are less common in the United States, the presence of a pressure cooker in an unusual location such as a building lobby or busy street corner should be treated as suspicious,” the bulletin said. Read more from this story HERE.