I think it would take quite a bit to bearproof a chicken coop. A motivated bear will tear through most anything. Now that he knows where food is, he will be back, especially if you replace the chickens. If the food is not there when he returns, he will move on. A co-worker of mine lives up in the hills of Evergreen at the base of the mountains. Lots of wildlife including bears in the area, so he's used to bearproofing everything, trash, cars, garage, etc. Once, he somehow missed a wrapper from a chocolate bar that was under the seat of his car. The bear got in and went through the seat. Not around, through.