The problem starts from the time the children first begin to realize they are individuals. They begin to make choices. Some are good and some are bad. They still know right from wrong as you taught them. Regardless of influence, they choose to do right or wrong.
Life is a series of choices.
Free will gives us that power. Instead of pointing fingers or looking for fault from inanimate objects, we should be holding ourselves accountable for our actions. That is personal responsibility. If I kill someone, it is my fault. It is not the gun's, not the knife's, not the bomb's and, certainly, not my parents' fault.