What does Gregors father think he left the room

Gregor's father believed he left the roomin order to do something bad..... to commit an act of violence.

"Just as I expected", said his father, "just as I always said, but you women wouldn't listen, would you." It was clear to Gregor that Grete had not said enough and that his father took it to mean that something bad had happened, that he was responsible for some act of violence.