I Found This Puppy Three Days Ago In My Front

I found this puppy three days ago in my front yard. He is about 10-12 weeks of age and I have been caring for the pup until we locate the owners. Well late this evening I went to check on him and I discovered that he'd been convulsing for a while due to the way he appeared to have been in and out of some mud. Plus he was convulsing, his head was forced back in this real tight pose and he won't stand on his own. It's 1a.m. where I live and I do not know what to do. Doctor, what do you think might be wrong with him?