A pressure cooker bomb “is not a high-tech device,” said Michael White, director of explosives and training with MSA Security, a consultant company, in an interview. Typically, such a device would contain low-level explosives inside a container that could withstand a great deal of pressure. The explosives would then be ignited with some type of power source, setting off the explosion.
Risk analyst Alexia Ash said the early signs suggest the attack was more likely perpetrated by home-grown terrorist, rather than a foreign network like Al Qaeda.
“We’re talking Al Qaeda inspired but not trained,” said Ash, head of forecasting in North America for Exclusive Analysis Ltd., an IHS affiliate that analyzes relevant political and violent risks around the world. “The person who made this type of weapon had some type of training or at least some type of practice. It wasn’t a Molotov cocktail, but it wasn’t a truck bomb. It was between the two. It’s low capability, but something that would require training or practice to produce.”
Law enforcement officials also renewed a call Tuesday for photos and video shot by race spectators, on the theory that somebody among the untold thousands of people who documented the scene has pictures of the bomber. Homeland Security officials asked departing passengers at Logan Airport on Tuesday to share their photos or videos of the finish line, said a law enforcement official familiar with the investigation.
Hundreds of officers fanned out across the city Tuesday, working 12-hour shifts in a show of force meant to reassure the public. “Obviously, you don’t really want to take public transportation right now,” said 23-year-old Shelby Zawaduk, while waiting at Park Street Station for a Green Line train. “But seeing the guards definitely makes me feel better.”
Police are also guarding specific areas around Boston they deem vulnerable, particularly Jewish places of worship and institutions, according to a Boston Marathon response plan obtained by the Globe.
Boston police assigned two officers to patrol the Consulate General of Israel at Park Plaza, and ordered officers throughout the city to randomly patrol 14 other Jewish institutions, including temples, hospitals, a day care center and a senior center. Officers assigned to the South End district were ordered to patrol Jewish campus organizations, such as Northeastern University Hillel and Boston University Hillel.
More than 140 officers were sent to patrol hotels across the downtown area and more than 100 were sent to guard the crime scene perimeter, according to the plan.
Boston police have said they have heard no specific threat. The plan, officials said, reflects overall concern police would have over any locations they deem vulnerable, because of their symbolic importance, their geographic location, or — in the case of Jewish institutions — their history as targets of terrorism.
Investigators on Monday had questioned a Saudi national, a student at a Boston-area university, who had been hurt in the explosion. US officials informed the Embassy of Saudi Arabia in Washington Monday night that the student was not a suspect and was cooperating with the investigation, according to Nail Al-Jubeir, spokesman for the embassy.
At Logan International Airport Tuesday morning, a United Airlines flight to Chicago was brought back to the gate after passengers expressed fear over two people speaking a foreign language, said aviation authorities. Passengers and bags were taken off the plane and re-screened, and two people were rebooked on a later flight, said United Airlines spokeswoman Christen David. Soon after, a US Airways flight arriving from Philadelphia was kept from the gate due to suspicions about a checked bag on the plane. Passengers were bused to the terminal. The bag was rescreened and cleared.
Traffic snarled around the 12-block crime scene in the heart of Back Bay, which remained blocked off for the investigation. Boston Police Commissioner Edward Davis predicted the area would remain closed for “a couple of days.” One law enforcement official briefed on the investigation said Copley Square presents a challenging crime scene. “We are taking evidence off the tops of buildings,” the official said.
More than 100 people from Boston police, state and federal agencies are working at the scene. Newspapers and websites around the world on Tuesday carried a montage of gruesome photographs of the carnage, but none was more upsetting than a simple snapshot of Martin Richard, the Dorchester boy killed in the blast, holding a hand-scrawled sign that said: “No more hurting people. Peace.”Continued...