Die right after the Count, no drops

First time accessing the Count boss fight in Act 1. After killing him something on the ground I couldn’t see suddenly drained my remaining life. I died as the Count death animation was happening. A scene began, but it stopped because of death screen. I didn’t get to see how that part ends, and I didn’t get any drops. I don’t know if there was anything quest related that I will need later. I tried to go back to fight him again, but I no longer have access to that waypoint. Not sure if there was residual AOE damage still happening on the ground. But loot and important drops need to still be accessed after such a key fight.