Maybe he was mad because he'd been having a temper tantrum all day and no one knew it but him. And to make matters worse, his own mother, who should have been there listening to him have a temper tantrum, was actually out in the world all day doing healthy things with people she loves.
Oh, that Bart.
***
What a rotten end to a beautiful weekend. You had posted about postponing Father's Day, and about looking forward to the weekend with your peeps, on the Morning Thread. After a weekend filled with travel and lake time and family, 9:30 would have been very late for me, too.
Still, you called him, and were willing to talk to him until he could sleep.
You are a great mom.
I would have waited until Monday. Seriously, I would have been sound asleep by 9:30. This brings to mind that old saying about the mother and the mixer: Good mothers let their children lick the beaters. Great mothers turn them off, first.

Maybe that is what is going on, here. Our sons are chronically exhausted from throwing temper tantrums their mothers no longer have time to schedule in. No one witnesses their tantrums anymore and so, they don't know when to stop. By the time their mothers finally call them, the poor things only have enough energy left to spout a few bad words and fall asleep.
SWOT. Excellent technique.
You are my hero.
Cedar