James Comey's firing as head of the FBI prompted shock, anger and chaos in Washington. In an excerpt from “Trump’s Showdown,” FRONTLINE’s season premiere, go inside Rod Rosenstein's role in that critical event, which began with a meeting between Trump, Rosenstein and Attorney General Jeff Sessions. “Trump’s Showdown” comes to PBS and pbs.org/frontline Tuesday, Oct. 2 at 9 p.m. EST/8 p.m. CST.