a checkpoint leading into the park. the gunman who allegedly wounded four people at a house party then fled into the woods. barnes served on front lines in iraq and may have served post-traumatic stress disorder. at least that's what some are saying given what happened. although there is no definitive link at this time. the big question is, what is the motive? what happened? why would a 24-year-old man go on a horrific shooting spree like this? it's a mystery that a lot of people want to solve, especially as we have so many people who sacrifice so much coming home from the iraq war. joining us forensic psychologist michael brannen. good to have you with us. we appreciate it so, in your -- >> thank you. >> in your expert opinion s this something that would indicate by any of the behavior or what you saw that it could be linked to ptsd? >> well, it certainly could be. with post-traumatic stress disorder, especially combat-related post-traumatic stress disorder, oftentimes what you find is people who have a heightened sense of danger in and reaction to danger.