You answered your own question earlier. Nothing has changed in terms of your interactions towards one another so he's leaving because he thinks nothing is ever going to change.
"I asked him if he was just going to stop speaking to me altogether. "
You shouldn't have said that. He perceives this as being "his" problem when you have an equal hand at causing his silence. He doesn't want to speak because he thinks it will lead to an argument. You have to SHOW him things are different with you. If you continue to act the way you have, you'll just get more of the same.
M-43 W-40 2D - 9 and 5
Emotion, yet peace. Ignorance, yet knowledge. Passion, yet serenity. Chaos, yet harmony. Death, yet a new life.