A look at the deadly Boston Marathon bombing - Article Photos 6/6

A sign calling for citizens of Boston to "Shelter in Place" is shown on I-93 in Boston Friday, April 18, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Elise Amendola)