Is he molting? When they molt - especially if is ISN'T really slow - they want to avoid contact and are miserable - so they tend to avoid others and can be irritable. Hens absolutely do this, and Some of my roos do this as well - again, especially when they are molting in the abdomen and sides where they tend to rub and the pins irritate them.
My hens frequently will hide in a nest box or be off by themselves with back pins, too, to avoid mating. For some reason, it seems chickens are molting earlier this year - and most of mine are molting HARD. (versus late Nov & December the past few years, and Sept - October for many years before - with straggles/consistently hard molters late Oct. or Nov.) This year, my early molters started in August!
I am wondering if we are in for a herd winter - or if the wonky weather and lots of rain (i.e. less sun than usual) is prompting the early molt?????