Military stress and tragedy at Fort Hood

My heart goes out to all the families recently affected by this tragic event at Fort Hood Texas. CNN is reporting that the suspect in this shooting case is a military psychiatrist (Maj. Nidal Malik Hasan) who was practicing at Darnall Army Medical Center at Fort Hood. Previously, he worked at Walter Reed Army Medical Center.

It's hard to imagine the level of stress some people must go through. According to this story, Hasan was to get deployed to Iraq. What caused this type of erratic behavior? Was it stress? The human mind is so complex that it's hard to imagine what Hasan must have been experiencing as a military psychiatrist.