The cause is anger. It all begins with a small fight then due to pride there is no confession of sin. Haman hated Mordecai because he would not bow to him. The Pharisees hated Christ because he excelled over them doctrine, and set the example to the people. But the Pharisees never let him go till they nailed him to the cross.
Hatred is a poisonous snake that lives in the blood.
With hatred comes mental murder. You do not have to commit a murder to be a murderer as God sees your heart and your motives. How many times we have heard that children have assaulted their parents. Such a monster was Nero, who caused his mother, Agrippina, to be slain. FBI statistics from 1997 showed about 1.5 percent of the country's murder victims that year were killed by their children.