Legally, he is responsible. The creditors can only take action against him - not against you.
If he wants you to pay anything, that is a matter between the two of you. If part of the expenditure was incurred by or for you then it is perhaps reasonable for you to come to an arrangement with him. However, if you don't pay him he would have to take you to Court to try and get a judgement against you. Whether he would succeed would depend on the judge, who would need to be satisfied that you had entered into an arrangement under which you were to pay him. If there is no such arrangement he might have difficulty proving to the Court that you have a liability, but you cannot be 100% certain of that.