Finally fooled it! When Snape left 12 Grimmauld Place, although his face didn't change much, his heart was very disturbed. He never expected that he would kill Dumbledore, but it was predicted by Anderson. No wonder that guy doesn't like to see me so much!
So Dumbledore should have known about it. Snape thought it was necessary for him to talk to Dumbledore about this, so as not to The content of this chapter is being updated...