The point is moot, now.
Samuel went into the chicks brooder, had them cornered, in a hostile stance. I grabbed him and restrained him. I shut the brooder before returning him to the coop.
Martha was standing there, didn't defend the chicks at all, though I have seen her launch at the other hens if they came close.
Later I was standing outside the door to the coop and the chicks started screaming. I looked and Samuel was chasing them around the coop, not giving pecks, but was in full out attack mode, focused on them like prey.
I took him out and dispatched him out of sight of the others. It's the first time I have had to do that task, and I cried.
I can now see a pattern, from an initial attack that left a chick unconscious with a head wound, then a second attack the next day with a worse wound, to the other examples of him being aggressive against the chicks, which I saw. None of the hens have done more than a short peck, none have chased the chicks.
Thanks for everyone's input.