If they are your neighbor I would introduce myself and let them know you noticed they left a cam on your property. If they seem like reasonable people I would let them hunt the edge of your property where the trail is. I think you are worrying unnecessarily about them shooting your animals. It is not even remotely likely. Hunters really do know the difference between deer and horses believe it or not. If they seem like jerks than warn them about tresspassing and that you will be pressing charges for future viloations. Good luck and hopefully you make some new friends. They may end up helping you out someday if the situation works out.