Both countries accused the other of firing the first shots as tensions boiled over on Thursday and reports of casualties began to emerge. ABC News' Britt Clennett reports. 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-uI8ixlVw1NWu_