Lt. Col Dave Grossman is the author of On Killing and On Combat as well as several science fiction books.In 1998 Lt. Colonel Grossman retired from the military as Professor of Military Science at Arkansas State University. His career includes service in the United States Army as a sergeant in the U.S. 82nd Airborne Division, a platoon leader in the 9th Infantry Division (United States), a general staff officer, a company commander in the 7th Infantry Division (United States) as well as the U.S. Army Rangers and a teacher of psychology at West Point.Grossman's first book, ''On Killing: The Psychological Cost of Learning to Kill in War and Society'' is an analysis of the physiological processes involved with killing another human being. In it, he reveals evidence that most people have a phobic-level response to violence, and that soldiers need to be specifically trained to kill. In addition, he details the physical effects that violent stresses produce on humans, ranging from tunnel vision, changes in sonic perception, and post-traumatic stress disorder.Grossman argues that the techniques used by armies to train soldiers to kill are mirrored in certain types of video games. The conclusion he draws is that playing violent video games, particularly Light gun shooters of the First-person shooter-variety (where the player holds a weapon-like game controller), train children in the use of weapons and, more importantly, harden them emotionally to the task of murder by simulating the killing of hundreds or thousands of opponents in a single typical video game.His second book, ''On Combat: The Psychology and Physiology of Deadly Conflict in War and in Peace'', is an extension of the first, intended to provide coping strategies for dealing with the physiological and psychological effects of violence for people forced to kill in their line of work (soldiers and police officers).Grossman uses blunt language that draws the ire of gamers - during the heights of video game controversy, he was interviewed on the content of his books, and repeatedly used the term "murder simulator" to describe first-person shooter games.Since his retirement from the Army, Grossman has founded the Killology Research Group and continues to educate law enforcement officers and soldiers in the techniques he has studied for improving outcomes in lethal encounters. He also speaks at civilian events on ways to reduce violence in society and deal with the aftermath of violent events such as school shootings.