Pentagon focuses on cause of Fort Hood shooting

The U.S. Department of Defense (DOD) is working to investigate the cause of Wednesday's shooting at Fort Hood, Texas, the Pentagon said Thursday.

Pentagon spokesman Steve Warren expressed the DOD's condolences, as well as his own, to the service members, military families and civilian employees affected by the shooting, which left four dead, including the shooter, and 16 others injured.

Investigators at Fort Hood are talking to personnel at the gunman's previous duty station "to determine the facts surrounding his behavioral health status," the official said. "Both DOD and the Army are focused on finding the root cause of this incident, comforting victims and assuring them our military communities are safe places to live and work."

Wednesday's shooting was the second of the kind in less than five years at Fort Hood, where Army Major Nidal Malik Hasan, a psychiatrist, opened fire on Nov. 5, 2009, killing 13 people and injuring more than 30 others.