Hi there! Most important thing when you are in that situation is to not leave the scene straight away because it is considered "hit-and-run" and it is a punishable offence! Adding on, that irresponsible act will further complicate matters and affect your car insurance. I'm pretty sure nobody wants that. Thus, it is highly advisable for you to stop the car at a safe spot and alight. You should wait for the owner to come back or alternatively leave a note with your details on it. Take responsibility of your action!
To find out more on the things to not do after an accident, check out this article: