Sometimes dogs can become skiddish for a lot of reasons. The main thing is to get him back to being around you guys. Make sure that he is fed often. Try using treats to get him to come to you so you can pet him. Make sure that you do not express anger towards him. Watch and see if anyone including neighbors have been treating him wrongly. If he used to be a loving dog, then most likely something someone did spooked him. You just need to show him love again. Doing things that dogs love, and showing him that your fine. Going for walks, treats, play time.
Have you tried taking him to the vet? There are a number of reasons a dog might develop a phobia from an unfamiliar smell to an unpleasant experience (even someone accidentally stepping on his paw or tail), but sudden personality changes are often health-related. If he's in pain for any reason, he doesn't understand why. He may think that he's done something wrong and thinks his humans are inflicting the pain, and so he runs away. Until he can be health-checked, be gentle and patient with him. Try not to make sudden movements or raise your voice, don't look directly in his eyes, and let him come to you. If he runs away, let him get his distance -- he'll come back and try again when he feels secure.