This photo released May 1, 2013, by the U.S. Attorney's office in a federal criminal complaint, shows fireworks, which the complaint said federal agents recovered from inside a backpack belonging to Boston Marathon bombing suspect Dzhokhar Tsarnaeva, found in a landfill in New Bedford, Mass. Three men who attended the University of Massachusetts at Dartmouth with Tsarnaeva, were charged Wednesday, May 1, 2013, in connection with the case. (AP Photo/U.S. Attorney's Office)

Photo by: Uncredited

This photo released May 1, 2013, by the U.S. Attorney's office in a federal criminal complaint, shows fireworks, which the complaint said federal agents recovered from inside a backpack belonging to Boston Marathon bombing suspect Dzhokhar Tsarnaeva, found in a landfill in New Bedford, Mass. Three men who attended the University of Massachusetts at Dartmouth with Tsarnaeva, were charged Wednesday, May 1, 2013, in connection with the case. (AP Photo/U.S. Attorney's Office)