Toyota Repair: Seized engine?, crankshaft pulley, gear teeth

Question
A good friend of mine gave me a 1992 Corolla last December. They were the only owners and it has about 117,000 miles. In mid-June, my husband was driving it on the highway at about 75mph when it suddenly started making a very loud continuous noise, like backfires. He shifted into neutral (it's an automatic), the noise continued and the car died. He started it back up, while in neutral still rolling down the highway, made the same noise and died again. He coasted to a stop, and tried to restart the car. It wouldn't turn over. All of the electric still functions (the lights dim), but the car wouldn't start, won't turn over - nothing. We checked the oil and water, all is okay there. The car never burned oil, never knocked or tapped. After consulting with a few people, we checked to see if the timing belt was missing - but it appears to be fine. Any ideas or suggestions? Thanks!

Answer
Remove and check the starter, it's possible that the starter failed and engaged while the engine was running and then seized up while engaged in the flywheel, after removing the starter try to turn the engine over at the front crankshaft pulley, if it can be rotated it's not the engine.  
After removing the starter for inspection it should be obvious if it is the problem, make sure the flywheel is inspected for any damage to the ring gear teeth.