ABC News’ Aaron Katersky breaks down what we know about the suspected gunman who opened fire on a July 4 parade in Highland Park, Illinois, on Monday. WATCH the ABC News Live Stream Here: https://www.youtube.com/watch?v=w_Ma8oQLmSM SUBSCRIBE to ABC NEWS: https://bit.ly/2vZb6yP Watch More on http://abcnews.go.com/ LIKE ABC News on FACEBOOK https://www.facebook.com/abcnews FOLLOW ABC News on TWITTER: https://twitter.com/abc #ABCNLUpdate #highlandpark #massshootings #abcnews