ABC News’ Phil Lipof spoke with ABC News contributor and former DHS official John Cohen on the “missed warning signs” in the Illinois shooting and challenges in tracking would-be shooters. ABC News Live Prime, Weekdays at 7EST & 9EST 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 #ABCNLPrime #HighlandPark #ParadeShooting #HomelandSecurity #JohnCohen #WarningSigns