The Iceman and why he killed
https://youtu.be/c4ZKlnfBopI
I watched the series on The Iceman and in particular this Youtube video shows exactly what triggers his anger.
It didn't take much and was calculated into the conversation by the interviewer to show Kuklinski what happens to him.
The damage he sustained from his early childhood fashioned him into what he was in adulthood, even though he confessed to his first killing at age 14.
I felt some compassion for him and you can see from his interviews that he is a deeply introverted and damaged personality. My dislike and fear of him soon extinguished as my fascination to uncover the why of him propelled me to watch the full series.
"After watching, you may feel some minds are better left unpenetrated."