Most of the people who are violent weren't socialize properly when growing up.
The next factor that contributes to the violence is poor parenting. These parents show no or little love to their children and also physically abuse them. So they grow and become angry easily.
The next factor is the failure pass subjects and matriculate to college and university. Research had shown persons who attend college and university are often less prone to do violence. These person are more occupied and have a future to look at.
Lack of jobs and responsibility. People who don't have job to buy their basic needs items are more likely to be violent. These people will get depressed and angry easily . The least thing that is said to them,which they may think is offensive.They may respond violently without a second thought.