http://listverse.com/2013/01/02/10-most-common-traits-of-potential-serial-killers/
http://www.psych2go.net/90-of-serial-killers-admit-to-killing-animals-before-killing-humans/
Respectfully, I beg to differ.
Well, let’s see there, 2 of your links are clickbait articles and the last is from PETA, who have an obvious agenda.
I’ll take the work of reputable psychologists over that any day.
https://www.psychologytoday.com/blog/witness/201205/homicidal-triad-predictor-violence-or-urban-myth