Or, it was false positives. It was TOO convenient that a unrelated nut just happened to do this around the time as Boston.
Yet the media (and president) have been silent over the bomb that was mailed to Sheriff Joe Arpaio the week before the Boston attacks. Media covered the initial incident, then nothing. No pledge from the president to use all the resources necessary to bring those responsible to justice (as he did in the Boston bombing case). President Obama doesn't care about Joe Arpaio.