Vincent Lisi transferred to Boston late this summer and inherited the massive probe into the Marathon attack and anyone potentially connected to the alleged plot carried out by Dzhokar Tsarnaev and his brother, Tamerlan.
Although Tamerlan was killed and Dzhokar arrested shortly after the April bombing, investigators are looking for potential accomplices. The Boston Globe said a federal grand jury recently heard testimony from Tamerlan Tsarnaev's in-laws.
"We owe that to the victims of the bombing," Lisi told the Globe. "Our focus, commitment, is that nobody in our office will rest until we've identified everyone that had anything to do with the bombing and make sure they face justice."
The Globe said Lisi came to Boston with a background in counterterrorism. He was previously posted in Yemen and was most-recently deputy director of the FBI Counterterrorism Division in Washington.