The soldier who shot 12 Dallas police officers and killed five last month had shown symptoms of Post Traumatic Stress Disorder after returning from Afghanistan, according to Department of Veterans' Affairs documents the Associated Press reported Wednesday evening.

The shooter, 25-year-old Micah Xavier Johnson was a former U.S. Army reservist and had said he wanted revenge for the recent deaths of two unarmed black men at the hands of police officers. Johnson, an African American, was killed by authorities July 7 after terrorizing peaceful protesters who had taken to the streets in downtown Dallas.

Johnson had sought treatment for anxiety, depression and hallucinations after he returned to the U.S. in 2014. He also reported hearing voices and mortars exploding, according to records.

On one occasion during a trip to Wal-Mart, police were called after Johnson had a violent PTSD episode.

"Veteran states hearing all the noises, fights and police intervening caused him to have palpitations, 'My heart felt like someone was pinching it while it was beating fast,'" the records state.

Despite the incident, Johnson was never formally diagnosed with PTSD. During an Aug. 15, 2014 doctor visit, a physician documented Johnson was "not acutely at risk for harm to self or others." On that date, records show Johnson also discussed erectile dysfunction and a troublesome childhood.

He had started seeing a psychiatrist, as well as taking a muscle relaxant, antidepressant, anti-anxiety and sleep medication. In October 2014, he requested suspending further PTSD evaluation as he felt better. That month he requested an appointment with the Dallas VA for a back condition, but gave up after not hearing back.

Dallas police confirmed Johnson had bomb-making materials, ballistic vests, rifles, ammunition and a personal journal of combat tactics at his home.

Police say people they interviewed have described 25-year-old Johnson as a loner.