Lt. Col Grossman began his career in the Army as a sergeant in the 82nd Airborne Division, then as a platoon leader in the 9th Infantry Division, a general staff officer, a company commander in the 7th (Light) Infantry Division as well as a paratrooper and graduate of Ranger School. He went on to become a professor of psychology at West Point.

In February 1998, Grossman retired from the military as a professor of military science at Arkansas State University. He is the author of "On Killing," an analysis of the psychological processes involved with killing another human being, and "On Combat," an extension of his first book 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.

Since his retirement from the US Army, he has been on the road almost 300 days a year, for over 19 years, as one of our nation’s leading trainers for military, law enforcement, mental health providers, and school safety organizations.

Today Col. Grossman is the director of the Killology Research Group (www.killology.com). In the wake of the 9/11 terrorist attacks he has written and spoken extensively on the terrorist threat, with articles published in the Harvard Journal of Law and Civil Policy and many leading law enforcement journals, and he has been inducted as a "Life Diplomate" by the American Board for Certification in Homeland Security, and a "Life Member" of the American College of Forensic Examiners Institute.