breaking news, deputy attorney general rod rosenstein has a new right-hand man in the russia investigation. this is an important step, rosenstein picking the veteran prosecutor ed o'callahan. he will serve as the acting principal associate deputy attorney general. this comes on the same day that the first sentence was handed down in the mueller probe. justice reporter lara jarrett joins me "outfront" on the phone with the breaking details. what more are you learning? >> reporter: erin, o'callahan is a verne federal prosecutor. he's prosecuted terrorism cases, high-profile ones, primarily in new york, but he now lands in the thick of perhaps the highest-profile investigation currently at the justice department as the special counsel deepens his probe into former trump campaign associates. but he's going to have way more on his plate. in fact, unlike many people at the justice department, o'callahan is going to be responsible for managing all of the units at doj, everything from the criminal division, down to, you know, justice progress.