I'm fairly sure it's his white "USA" hat, in shadow.

But it's very oversized and square looking Like an old fashioned hat conductors wore on passenger trains. Ticket please.

Look closer. It's the same color/shadow as an architectural feature (molding) beyond his head. Look at the line in the molding and see where it continues in the shadow up to the shape of the hat. I've drawn a line on the second image here to show the edge of the hat.

Gotcha. I have old eyes, but it looked like a train conductor’s hat!!

Yes, at first glance it sure did. But I'm a semi-pro/semi-amateur photographer, so looking closely at and through images is something I do regularly. Trained eye, and all that. And no, I do NOT like examining photos of his decaying carcass. 😝

oh my goodness, of course it's a USA hat, thank you! and they do make those white "USA" hats kind of large, which adds to its odd look

Good eye

Looks too big for his head

Here it is on a model. It looks too big for his head, too.

No this one does not look took big.

I wonder if he could pass the dementia test today? The one he, Gavin & Koko aced.