National Guard soldiers at a roadblock in downtown Boston today.(Spencer Platt/Getty Images)

• Investigators say they have no suspects in yesterday’s Boston Marathon attacks, and are asking people who were in the area to send in photographs and video. A circuit board and the remains of two pressure-cookers believed to have been packed with shrapnel have been recovered from the blast sites. [Boston Globe]

• “We had no idea what was coming,” Boston Medical Center ER Dr. Ron Medzon said of the scene after yesterday’s attacks. [WBUR]

• A 16-year-old student at Mesivta Ateres Yaakov, a yeshiva in Long Island, was arrested for making a bomb threat against the school. “Even though he made a threat, we still care about him,” said the school’s assistant principal, Rabbi Yossi Bennett. [NYP]

• Meanwhile, Gabby Giffords was in Washington to lobby for gun control legislation. Her husband, Mark Kelly, told a breakfast roundtable the couple expects to raise $20 million to spend pushing the issue in the 2014 midterm elections. [The Hill]