Police Converge Mass

A message calling for citizens of Boston to "Shelter in Place" flashes on a sign on I-93 near the Zakim Bridge in Boston Friday, April 19, 2013. The Boston area was all but paralyzed as a manhunt continued for Dzhokhar Tsarnaev, one of the two suspects in the Boston Marathon bombing who authorities say killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left his brother, Tamerian Tsarnaev, dead. (AP Photo/Elise Amendola)