Passage: By the 17th century the Rosenbergs had died out, and Holy Roman Emperor Ferdinand II gave the dominion of Krumau to Hans Ulrich von Eggenberg, naming him Duke of Krumau.  After the death of Hans Ulrich's son, Johann Anton I von Eggenberg, the castle was administered for the period between 1649 and 1664 by his widow, Anna Maria.

Question: Which event caused Anna Maria to begin adminitering the castle between 1649 and 1664?
the death of Hans Ulrich's son