Videos of the crowd are being examined by investigators to attempt to identify two suspects in the Boston Marathon bombing. Also in the evidence are part of a pressure cooker top and a piece of circuit board believed to be part of the explosive devices. The bombs are believed to be improvised explosive devices (IEDs). Pressure cookers were filled with nails and ball bearings for shrapnel, an explosive compound (probably black powder) and an ignition mechanism. This particular type of IED is taught in terrorist camps in Afghanistan and there are instructions on the internet.
Common injuries that occur from IEDs can include overpressure damage to the lungs, ears, abdomen and pressure-sensitive organs, fragmentation injuries from shrapnel, impact injuries from being thrown into another object, and thermal injuries including burns to the sinus and lungs.
The Department of Homeland security has a list of advice on how to handle a possible IED attack. First and foremost, watch out and report any suspicious activity. Trusting your instincts and erring on the side of safety can prevent an incident from even happening. You should also know the emergency procedures for your place of work. Know where the emergency exits are and the location of the nearest hospital. Even basic knowledge of first aid can save lives while waiting for first responders.
As was the case in the Boston bombing, many times a secondary explosive is planted near the first one. This is designed to inflict maximum casualties to first responders and those rushing to investigate the first explosion. In addition to designed secondary bombs, secondary explosions can occur from cars, gas lines, or other flammable materials that might be ignited by the bomb. It is paramount to get out of the area as quickly as possible and to a safe spot.
The Wall Street Journal, Video Provides Clues to Bomber: http://online.wsj.com/article/SB10001424127887323809304578428601821162728.html?mod=WSJ_hps_LEFTTopStories
The Wall Street Journal, Man Is Arrested in Ricin Scare: http://online.wsj.com/article/SB10001424127887324493704578428681727849900.html?mod=WSJ_hps_LEFTTopStories
The Washington Post, Arrest Made in Ricin Case: http://www.washingtonpost.com/politics/letter-to-obama-containing-suspicious-substance-intercepted-by-secret-service/2013/04/17/dd4b2152-a76e-11e2-a8e2-5b98cb59187f_story.html?hpid=z2
The Department of Homeland Security, IED Attack Fact Sheet: http://www.dhs.gov/ied-attack-fact-sheet