I submit that he had a mental illness that went untreated and ignored. It strikes hardest young ment between 26 and 30 something and subsides somewhat with age. He exhibited classic symptoms. Medication intervention would have allowed him a chance and the people he killed a chance.
Something wrong with the chemistry in your brain is not evil. Look at the photos of him as a young boy before the illness manifested. He was overtaken by a cruel disease.