If I was a betting man, I would say your RIR got his injuries from a good old fashioned show down with a hawk.
I witnessed the tail end of a battle between my RIR and a hawk.
The RIR lost in the end, but he went down swinging, all the other birds survived.
The hawk in question was rumored to have died from lead poisoning, as he was never seen again.
I always keep a RIR around for the free range flocks.
Just my .02