Can creditors come after distributed 401K funds of a deceased person?

Typically, no they cannot.  Creditors can only make claims against the assets of an estate.  Since most 401K's provide for a designated beneficiary, the proceeds would be payable directly to that beneficiary and therefore do not become a part of the estate.

However, if no such beneficiary was designated or the beneficiary pre-deceased the owner of the 401K (and there is no contingent beneficiary listed), then in that event, the proceeds are paid into to the residuary estate.  As such they would then become an asset of same and subject to creditor claims.