Been around chickens a long time but gotta say this is the first I've heard of a cougar attacking them. Must be a really desperate lion to waste the energy on something that small. I'd look for it coming back. Might want to check the local laws on dispatching one. Often animals like that have different rules than more common nuisance animals. Your states wildlife management might even want to come out and remove it for you. Honestly I would give them a call and explain it's attacking your livestock. I'd almost bet they send somebody out with a large trap.