What are some of the major theoretical explanations given for the rise of this social phenomenon and which approach is best suited to Leytons analysis?

Answer ONE of the following two questions.
For this assignment – each chapter would be a case study. So I would pick one serial killer and one mass murderer and focus on them. However, it is important to recognize the similarities and differences between one case and the other. But begin your essay with a general discussion of serial killers and mass murderers – what are their various characteristics – how are they the same and how are they different? Then go onto discuss the case studies followed by a discussion of the theoretical aspects – biological, psychological and sociological/anthropological explanations. Why does the US have a disproportionate number of these killers? And finally, place the rise of the modern multiple murderers into the wider historical
Gilmore, Mikal. Shot in the Heart. (1995)
Leyton, Elliott. Hunting Humans.
Dyer, Gwynne. War. (2005)
Stoessinger, G. John. Why Nations Go to War. (11th edition)
The course manual is attached as additional material. 1) Using at least two case studies discuss some of the differences between serial
killers and mass murderers. Finally why, according to Leyton, do most serial killings and mass murders occur in the United States?2) Drawing on examples from your textbooks and course manual and text, discuss some of the significant social influences that can lead to aggressive/non-aggressive behavior