I've got an '85 Sentra 5 speed, 4 cylinder.

I've got an '85 Sentra 5 speed, 4 cylinder, gasoline engine, with 210,000 miles. I was driving tonight, going about 30mph, when all of a sudden I started hearing a grinding noise coming from under the hood, it started getting louder, and then the engine died. I pulled over and opened the hood, and nothing seemed unusual or out of place. Radiator fluid was low, and I have had a slow and small leak in the radiator lately, but the oil was full and just changed last week. I tried starting it again after about 5 minutes, and the starter was turning over, with plenty of voltage, but it wasn't turning over the engine, and there were weird clicking and light grinding noises. I left it sit. My immediate thought was that maybe the timing belt or chain snapped.I'm not well versed on this, especially changing one of those if that's the case. Also, I don't see why, if for example, it overheated with no warning light, the engine wouldn't at least turn over. Any help would be greatly appreciated!