"He who makes a beast of himself, gets rid of the pain of being a man"
Samuel Johnson (poet, writer)
We are only inches away from being more beast than man when we leave behind our social doctrines to commit murder and harm to others. So, why do some men become more beast than man?
It's easy to generalize about serial killers, but statistically they are from low to middle income families, white males and in their 20s to 30s. They also display 3 characteristics young in life that are warning signs; they torture animals, set fires and wet their beds. Many were physically and/or emotionally abused. They have a preoccupation with police and authority figures. They may have even tried to be come officers or security guards.
The psychopathic nature of a serial killer shows that they do not know how to have relationships or to communicate, but have learned to mimic the process. They appear to enjoy not only mimicking, but acting as if they are in their own play. They cannot separate fantasy play from reality, and in the case of Ted Bundy he announced "I am disguised as an attorney today." They especially like to imitate authority figures.
Although we know that a great deal of the population has suffered trauma, brain injury, chemical imbalances, and abuse, they are not serial killers. So, why are a select few? There is a dynamic that seems prevalent; that these men had bad family situations and did not have a male figure relationship that was good. They may have received little nurturing. It was found that in some Eastern European orphanages, babies that weren't held or comforted, became apathetic and antisocial/psychopathic, as many American families hoping to adopt them later learned. There is a window of opportunity to learn compassion and it begins as a baby.
Some doctors have discovered that there is a genetic aspect that cannot be neglected. In tests of inbreeding with violent mice, they produced violent offspring. There is also a running theme of heavy alcohol use to relieve anxiety and depression.
How does this perfect storm form that creates someone capable of killing and torturing fellow man? My guess is enough time inside their own heads to form assumptions that are illogical and distorted, such as "people are in my way," or "everyone is weak but me," and being able to congregate all mankind into a refuse pile in one's mind. It's a bit like how hate crimes can occur with generalizations and seeing others as less than or unworthy.
We have had serial killers throughout history and they will continue on. If we are lucky enough to have a mental health system that catches the early warning signs as a child, we might prevent future scenarios. For now, man-beast exists in the form of Dahmer and Gacy, Bundy and Gein, and they are the things that nightmares are made of.