Rapid change of brake symptoms

Without warning, one morning, I drove 100 feet and braked on a downhill grade. I heard a heavy thumping, probably once per tire rotation, from the left front. I tried to diagnose it or change it by braking more heavily from 20 mph. After a dozen attempts, including backing up and braking, it was gone. The next morning, this repeated, but during one braking, there was a loud thunk (sharper than a thump) and the truck shuddered. Now the thumping is gone but I have pads scraping the rotor once per revolution quite audibly. I pulled the wheel and removed the caliper. Pads are good and the pitons are free. The rotor surface was OK on the inside, but scored on the outside. Since I have driven only a couple miles since all this began, I don’t think I warped the rotor any farther than it already was. I am suspicious that the loud sounds were really wheel bearing related. This is a 4WD version, but I was in 2WD during all this. Final note: rotors and pads have been replaced in the past (once in 150K miles) but nothing else. I also found thin rust pieces flaking onto the ground when removing the caliper. I’m guessing it needs an A-to-Z brake job, but would like to get other opinions.