White House chief of staff Reince Priebus wanted a top FBI official to dispute media reports that President Donald Trump’s campaign advisers were frequently in touch with Russian intelligence agents during the election campaign, a White House official says. The banned chemical weapon VX nerve agent, considered by some experts to be the nastiest of nerve agents , was used to kill Kim Jong Nam, the North Korean ruler’s outcast half brother who was attacked by two women who rubbed the substance on his face.