In what is a shocking, bizarre, and grotesque act of violence, a man has beheaded his 5-year-old sister, stabbed his 17-year-old sister, and was only prevented from murdering his 9-year-old sister when cops shot him dead.

Kerby Revelus, a 23-year-old former con who was said to be trying to turn his life around, suddenly went berserk with a knife and killed two of his sisters, injuring a third. As cops entered the house to confront him, he beheaded his youngest sister in front of shocked cops.

Not only do I feel sorry for the family – the girls who have lost their lives and the parents and surviving sister who have to live with the grief – I also feel sorry for the cops who experienced this terrible crime taking place.

What makes people turn violent at the drop of a hat? We all have troubles, some big, some small. Most of us even experience extreme sadness or depression at some point in our lives. But why do some people react to it by lashing out and hurting others?