I'm sorry a predator has found your chickens. The harsh truth is it will be back. I've been in your exact situation a long time ago...my whole flock was decimated. I chose to stop raising chickens and ducks at that time. Fast forward 15 years, I wanted to start raising chickens again, but was determined that we would build them a home that was as safe and secure as we could make it...and we did (If you are interested in what we built, please see my coop article). Before you give up on raising chickens, here are a few things I'd recommend to improve the security of your coop.
1. Bury a Hardware Cloth apron around the whole coop and run.
2. Replace all chicken wire with Hardware Cloth (use the "U nails" to attach it, not staples).
3. Electric Fence, I can't stress enough how important I believe an electric fence is. It can be as simple as metal posts with plastic insulators or you can build an actual fence with cemented posts. You can also choose to attach the insulators directly to the coop and run. I'd go with a higher joule fence charger, you want the predator to feel pain when they touch it, not just a jolt. Remember that some predators can jump a short fence. We have so many different predators here in Western North Carolina, including black bears that I went with a 13 joule fence charger and we built a 5.5 foot fence around the coop and run. If cost is a factor in your decision and you can't build a fence, I'd go with running the hot wires directly on the coop, but I would go all the way up to the roof and over the top of the run. You would need to at least get the round metal fence posts to go around the coop so that the hot wires went and close to the ground as allowed to keep the predator from getting under the coop.
4. Outdoor solar lights around the coop area as they act as a deterrent when a predator approaches.
Amazon has them for a reasonable price. If you get the ones with a 10 foot radius you would probably only need 4.