Shane Tamura drove across the country with a semiautomatic rifle and then carried out a mass shooting on Monday in the building that's home to the NFL's offices, officials said. Subscribe to ABC News on YouTube: https://abcnews.visitlink.me/59aJ1G Watch 24/7 coverage of breaking news and live events on ABC News Live: https://www.youtube.com/watch?v=gN0PZCe-kwQ&ab_channel=ABCNews Watch full episodes of World News Tonight with David Muir here: https://youtube.com/playlist?list=PLQOa26lW-