Suffolk County District Attorney Daniel F. Conley speaks as FBI Special Agent in Charge of Boston Vincent B. Lisi, left to right, Boston Mayor Marty Walsh and Boston Police Commissioner William B. Evans, far right, look on during a joint news conference at the Boston Police Department's Headquarters Tuesday, June 2, 2015, in Boston. A man under surveillance by a joint terrorism task force was shot and killed outside a pharmacy Tuesday after he lunged with a knife at a city police officer when asked to drop his military style knife before the officer and an FBI agent opened fire. (AP Photo/Stephan Savoia)
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