I think that the primary reason that David Berkowitz got all psycho and all was because he spent the first 18 months of his life in an orphanage where he received very little love.
But, why did he commit that particular crime you ask? It was because it was how he envisioned his primal scene, that is, the scene of his conception. His mother was not part of a couple, she no doubt got pregnant after going out on a date; the same as all those young people who were shot.
No, I am not blaming the mother or the people who were on dates.
What do you think?