Yep all those Viet Nam vets been dying and aging out :

Arthur Shawcross, who killed 12 people and was a Vietnam veteran.

Leonard Lake, who served in the Marine Corps in Vietnam and suffered a psychological breakdown in Da Nang; he later committed multiple murders.

And many others

Gary Ridgway , Joseph Ernest Atkins , Fernando CotaArthur Shawcross aka ‘The Genesee River Killer’ Joseph James DeAngelo aka ‘The Golden State Killer’ Gary Ridgway aka ‘The Green River Killer’ William Bonin aka The Freeway Killer' Randy Kraft aka 'The Scorecard Killer' Leonard Lake Gary Lewingdon Ronald Gene Simmons Joseph Ernest Atkins Kenneth Lee Boyd Gary Bradford Cone James Floyd Davis Phillip Carl Jablonski James Rodney Johnson James Allen Kinney Leonard Marvin Laws Darrell Mease Michael Andrew Nicholaou Gary Lee Roll Morris Solomon Jr. Russell Wayne Wagner Ward Weaver Jr. Dan White Marvin Bieghler David Livingstone Funchess William Mentzer Larry Wayne White John Dwight Canaday David Knotek Jeffrey Don Lundgren Roy Lewis Norris

(David Berkowitz ("Son of Sam"), who was a U.S. Army veteran and served in the Persian Gulf War (not Vietnam), but his case is often linked in discussions about military training and violence.)

https://www.crimeandinvestigation.co.uk/article/was-the-vietnam-war-responsible-for-creating-a-generation-of-serial-killers

But you ignore my question of Intellectual improvement ?