A Pennsylvania man, who was known to investigators when he was a teen as being involved in the planning of a “mass casualty” incident, has been arrested in an alleged terror plot. Get a fast-paced look at the latest from the border to Main Street to the White House on "NewsNation Live with Marni Hughes." Weekdays starting at 9a/8C.#NewsNationLive NewsNation is your source for fact-based, unbiased news for all Americans. More from NewsNation: newsnationnow.com Get our app: trib.al/TBXgYpp Find us on cable: trib.al/YDOpGyG How to watch on TV or streaming: trib.al/Vu0Ikij