I think this THUG may well have had some type of undiagnosed mental illness such as bi-polar disease. It would NOT (as far as I know) show up in an autopsy but could help explain his behavior. He was displaying some sort of manic, king-of-the-world, “I’m indestructible” behavior starting (at least by then) with his strong arm robbery and continuing with his walk down the middle of the road and encounter with the policeman.
He was simply a THUG coming into full bloom as a monster.
“Top o’ the world, Ma!”