I think that transparency is key here. He hasn't been transparent with you about his announcement plans, or with the team about you leaving. I recommend being

I think that transparency is key here. He hasn't been transparent with you about his announcement plans, or with the team about you leaving. I recommend being honest with him and the team. Tell him that you'll be announcing your departure to the team today. You could even say that you want to announce it together with him. If he doesn't want to be there, then that's fine too. But it's normal to want to say goodbye, grab lunch / drinks together, or whatever when leaving a job. He doesn't need to be prescriptive about this. I've had people leave my startup, and I've had to fire people. I am telling you right now, it's so much better for morale if someone leaves, then gets fired. It sounds like this guy is taking it personally and is worried his reputation of having someone on his team leave. Sounds like you're making a good move, by moving on. Again, I would just be honest about your intentions and then deliver the news to everyone.