Perhaps it was inadvertently and he is absolved from exile - דלמא בשוגג ונקה מגלות
Summary:
One is חייב גלות (even) for a belated death if there is no concern for הרוח בלבלתו. There are several possibilities that one is חייב (גלות) (and) ד' דברים even by a שוגג.
He stole a condemned ox and slaughtered him, he pays the payments of four and five - 'גנב שור הנסקל וטבחו משלם תשלומי ד' וה
Summary:
A שור הנסקל can be sold to a gentile, and the monies are not אסור בהנאה, and additionally according to ר"ת a שור הנסקל is not אסור בהנאה while it is alive.