As people try to figure out a possible motive behind the Ft. Hood shooting suspect's devastating actions, familiar questions arise about mental illness and the unseen wounds of war.

According to investigators at Ft. Hood, unstable mental health may be a "fundamental underlying cause" of Specialist Ivan Lopez's shooting rampage. This week's attack left four dead, including the shooter, and wounded 16 others. 

Lopez had been seeing a military psychiatrist and was being treated for depression and anxiety, and yet, there seemed to have been no prior warnings.

While a lot of progress has been made in identifying and treating mental health issues in the military, this incident has — once again — raised some difficult questions about how best to evaluate and deal with mental illness among service men and women.

To help sort through those questions, we're joined by two southern California mental health professionals who are also both military veterans themselves.

Dr. Kimberly Finney is a board certified clinical psychologist and clinical associate professor at the USC School of Social Work. She is also a retired U.S. Air Force officer. Joseph Costello is a clinical social worker and Team Leader at San Marcos Veterans Center, Department of Veterans Affairs. He is also a retired Army reservist.