WASHINGTON—The threat from multiple homemade bombs detonated nearly simultaneously to kill or maim as many civilians as possible has been a hallmark of militant groups in recent years from Iraq to Israel and Afghanistan and Russia.
But until Monday at the Boston Marathon finish line in Copley Square, such street-level bombings targeting sidewalk or marketplace crowds had not taken place on American soil.
US law enforcement and intelligence officials across the country and overseas, scrambling to identify the source of the explosives, are now worried that the marathon sidewalk bombing could mark a new chapter in the struggle to secure the American homeland.
“We’ve seen this around the world, but what is so concerning about this is that it hadn’t happened here, not like this. Until yesterday,” said a senior homeland security official in Washington.
The Boston bombs were packed into pressure cookers and hidden in backpacks or duffel bags, according to multiple press accounts citing unidentified sources, another similarity with some Mideast attacks using “improvised explosive devices,’’ or IEDs.
One of the bombs used in a foiled attack in New York’s Times Square in 2010 was fashioned from a pressure cooker. A joint warning issued by the FBI and the Department of Homeland Security in 2010 said pressure cookers has been used for bombs in multiple attacks in Afghanistan, Pakistan, India, and Nepal.
Reports from medical staff at Boston hospitals who treated victims in the marathon attack indicate the bombs in this case were packed with BB’s, nails, and other projectiles intended to maximize human carnage. That contrasts with the large truck bombs that were used in Oklahoma City in 1995 and in the garage of the World Trade Center North Tower in 1993, which were intended to inflict damage on buildings, as well as people.
IED’s pack a much smaller punch, are cheaper, and easier to carry. They have been used in Iraq and Afghanistan with devastating effect on American troops in convoys of military vehicles.
No one has taken responsibility for the twin bombings on Boylston Street that killed three people and injured more than 150 near the Boston marathon finish line.
A senior US law enforcement official in Washington added that the fact that no group has taken responsibility has officials speculating that it might not be the work of a well-known international terrorist group like Al Qaeda, Hezbollah or one of its affiliates but a domestic group or individual inspired by the hallmark tactics of terrorist groups in recent years,
The Pakistani Taliban also said in a statement it was not responsible for the attack, unlike the attempted car bombing in New York’s Times Square in 2010 that it claimed responsibility for.
But officials in Washington have been warning about the possibility of so-called improvised explosive devises in recent weeks.
In late february the White House established a new task force housed in the Department of Justice to apply the lessons learned from years of dealing with so-called improvised explosive devices—some large and powerful and others more limited in scope like the ones apparently set off on Boylston Street yesterday.
“The threat from IED use is likely to remain high in the near future, and will continue to evolve in response to our abilities to counter them,” according to a new strategy approved by President Obama on February 26.
“A whole-of-government approach that integrates Federal, state, local, tribal, territorial, private sector, and global participation in counter-IED activities will best position the United States to discover plots to use IEDs in the United States, or against U.S. persons abroad, before those threats become imminent.”
The 2010 warning from the FBI and Homeland Security said “terrorists can exploit the innocuous appearance of easily transportable items such as pressure cookers to conceal IED components. Placed carefully, such devices provide little or no indication of an impending attack.”
“Alertness and quick reaction to discovery of such concealment devices in unusual locations or circumstances can improve chances of early detection and prevention of an attack,” the warning continued. Potential indicators of a pressure cooker configured as an IED include protruding wires or fuses, unusual smells such as chemical odors, and wetness or unusual stains on a container.
A magazine published during the last decade by Al Qaeda provided bomb-making tips that included using pressure cookers. Instructions for building such bombs also are contained on other websites, including one site that bills itself as an ``anarchist cookbook.’’