Yes they will be back. Coyotes will do anything and everything to get to a food source. We had a pack find our coop 3 years ago. They dug under the coop and 3 feet under the buried fence and ripped open the door and killed every last one of them.
We learned from this and didn't use chicken wire anymore, and put heavy rocks buried all around under the coop and fence.
I live in Michigan right on the edge of 600 acres that a friend of mine lives on. There's a large pack of coyotes that prowl around. They know I have chickens. They got in my neighbors coop and wiped out their flock and moved onto mine. I have a chain link dog fence around my run that's buried a couple feet. I also have large stones buried and stacked about a foot high around the perimeter. Because my run is only 5.5 feet high, I also have the top fenced. Coyotes have trie countless times and haven't been able to get in. The crafty coons haven't been able to either. The foxes stopped trying to dig under. The hawks can't get in. I have predator proofed *knock on wood* my coop and it didn't take too long. I would highly recommend dog fence, and if you're worried about raccoons reaching their hands through, wrap the inside in fencing too. The stones buried and stacked around the outside have really helped too. Nothing has been able to dig under.
In the meantime, I would grab yourself a .22 or a .17 with either ballistic tips or hollow points. They may seem small caliber but those .17s really pack a punch.
And this may be an old redneck wives tale, but if you kill one, hang it from a tree nearby. When the pack sees its member, they won't ever return. That's what I've heard at least.