BOSTON (AP) — Every time the widow of suspected Boston Marathon bomber Tamerlan Tsarnaev leaves her parents’ house, federal agents watching the residence follow her in unmarked vehicles.

Federal authorities are placing intense pressure on what they know to be the inner circle of the two bombing suspects, arresting three college buddies of surviving brother Dzhokhar Tsarnaev, and keeping Tamerlan’s 24-year-old widow, Katherine Russell, in the public eye with their open surveillance and leaks to media about investigators’ focus on her.