A skillful event is one that is not accompanied by craving, resistance or delusions; an unskillful event is one that is accompanied by any one of those things. (Events are not skillful in themselves, but are so called only in virtue of the mental events that occur with them.)
Therefore, the law of Karma teaches that responsibility for unskillful actions is born by the person who commits them.
Karma is the law of moral causation and is a fundamental doctrine in Buddhism.
In this world nothing happens to a person that he does not for some reason or other deserve. Usually, men of ordinary intellect cannot comprehend the actual reason or reasons. The definite invisible cause or causes of the visible effect is not necessarily confined to the present life, they may be traced to a proximate or remote past birth.
In other words, it is the result of our own past actions and our own present doings. We ourselves are responsible for our own happiness and misery. We create our own Heaven. We create our own Hell. We are the architects of our own fate.