Micah Johnson, the U.S. Army reservist who shot dead five Dallas police officers last month during Black Lives Matter protest, showed symptoms of post-traumatic stress disorder (PTSD), according to health documents obtained by the Associated Press. Doctors, however, reckoned that Johnson did not pose harm to himself or others.

Johnson complained about experiencing panic attacks — a symptom of the disorder — after serving nine months at a base in Afghanistan in 2013, the AP reported. However, Johnson was “not acutely at risk for harm to self or others” and he was “not felt to be psychotic by presentation or by observation,” one of his health records from Aug. 15, 2014, showed. The following September, Johnson went to a psychiatrist and was further evaluated for his PTSD symptoms. However, the doctor said Johnson’s mood was “better.”

The 25-year-old reservist’s case has thrown spotlight on PTSD that affects some of the army veterans. People of any age can develop PTSD after their exposure to life-threatening experiences and trauma. According to PTSD Foundation of America, 1 in 3 returning troops are diagnosed with serious PTSD and less than 40 percent seek help.

According to statistics provided by the U.S. Department of Veterans Affairs, about 11 to 20 out of every 100 veterans who served in Iraq War have PTSD in a given year. Twelve of every 100 Gulf War veterans have PTSD and about 15 out of 100 Vietnam veterans were diagnosed with PTSD at the time of the latest study in the late 1980s. According to estimates, about 30 out of every 100 Vietnam War veterans have had PTSD in their lifetime.

PTSD symptoms include flashbacks, nightmares, anxiety, depression, aggression, and insomnia, suicidal or unwanted thoughts.

Like most mental illnesses, there is no cure for PTSD. However, the symptoms can be controlled with therapies and treatments, such as medications or psychotherapy or sometimes both. However, there is no definite approach when it comes to treatment of PTSD. Some people respond better to some treatments compared to others. PTSD patients’ personality, the kind of trauma, severity of symptoms and support system also affect the efficacy of a given treatment.