talking with a terrorism expert who joins us from liverpool, england. thank you so much for talking with us. first of all, talk about the hero of the story, the officer who put his life on the line to save others. this could have ended much worse than it did if it were not for him. what are your thoughts? >> sums up -- i'm a former police officer myself. it shows the dangers they face and the sacrifices they make to keep us all safe. regardless of which state you are in. i mean, it's tragic this happened. but, his actions have made most, we'll find out in the full investigation, he may have saved lives. >> let's talk about what happened. officials knew of the suspect. they didn't know he was radicalized, there was no indication he was going on attack. this shows how difficult this is, this situation, this ongoing