Have you checked the adbmon for spur marks? I highly doubt the silkie did this. I think once the silkie saw the blood then it went to eat it or investigate. That's why he has blood all over his face. Your large cockerel was likely defending the flock from something when he lost his life.... I'm very sorry for your loss. But I highly doubt the silkie did this. He just went to investigate after your bird was already gone. Very natural. And normal for them to do if they see blood.