Acting U.S. Attorney for the Eastern District of New York, Mark Lesko, will replace John Demers on an interim basis as Assistant Attorney General in charge of the National Security Division at the U.S. Department of Justice in Washington, a source familiar with the matter tells News 4. Jacquelyn M. Kasulis, currently the acting Chief Assistant to Lesko in the Brooklyn U.S. Attorney’s office, will become interim U.S. Attorney, the source said.