SALISBURY, Md. - Authorities say 34-year-old Army Spc. Ivan Lopez gunned down three people and wounded 16 others before taking his own life on Wednesday.
Military officials say he had a history of depression, anxiety and other psychiatric disorders.
Lopez was being examined for Post Traumatic Stress Disorder, or PTSD, which is the mental illness that can be caused after being exposed to a life-threatening event. 47 ABC spoke with a local psychologist who deals with PTSD about what someone goes through.
"You feel like your life is threatened and that results in for many people, [but that's not with everyone]," said Dr. Leslie Donnelly. "[Symptoms include] re-experiencing the event and flashbacks."
Dr. Donnelly says about 10 percent of people who are exposed to a life threatening event develop PTSD. Treatment includes psychotherapy.
Reports say Lopez served four months in Iraq in 2011, but that his traumatic brain injury was "self-diagnosed."