I'm trying to use the word astonished in a sentence but to convey that I am surprised at a negative outcome. Is there a better word for this than astonished?

Example: I was astonished at the lack of respect Joe showed to his parents.

Is there a better word for the following example than astonished?

I was astonished at the lack of respect Joe showed to his parents.

I’m trying to use the word astonished in a sentence, but I want to convey that I am surprised at a negative outcome. Here, the lack of respect towards one’s parents is the negative part, but astonished is neutral, not negative.