I bet that somehow a fighting cock was introduced into his flock. A lot of people don’t know what they are and don’t distinguish them from ordinary chickens.
Fighting cocks have spurs, long sharp claws, coming from the back of their legs, and they are bred to fight and kill.
They are selectively bred for aggression, killer instinct and survival. They must be segregated from other animals when they aren’t fighting.
So, it was the pit bull of poultry, you're saying.
Even “ordinary” roosters often have nasty spurs.