what are the factors (social, environmental, mental etc.) that lead someone to become a serial killer (in a psychological sense). Are there any limitations in previous research literature on serial killers that could be explained in a new study.

what are the factors (social, environmental, mental etc.) that lead someone to become a serial killer (in a psychological sense). Are there any limitations in previous research literature on serial killers that could be explained in a new study. Please also design a study that would test (without actually carrying out the study) how people become serial killers [longitudinally]. What paradigm best describes the development of a serial killer (i.e., social, cognitive, clinical etc.). 
Please include Scholarly journals/citations (empirical studies if possible)