Manson has a history of manipulative and controlling behavior and has a record of mental health issues, including schizophrenia and a paranoid delusional disorder, Robles said.

CNN: STORY HIGHLIGHTS

Another risk factor is a condition called delusional disorder -- and in particular the "persecutory type" -- that causes people to believe that someone is plotting against them, Rossiter said.

CNN: Insights on why people 'snap' and kill