heartbroken

after 4 days of nursing my poor sick calf "the situation" he died yesterday of unknown causes. He has been eating well the whole time, and his manure looked normal. Had antibiotics. Was kept warm through the chilly nights. The ranchers next door had looked at him just the day before and said that he looked good, no signs of pneumonia. I just wonder what went wrong :( makes me so sad, I tried everything to make him better! Rip "the situation".