Strange that it came a fair old time into the flight. Could it have been caused by a bird strike for example?
Doubtful IMO, but not out of the realm of possibility.
Birds of pray may attack a UAV, however as one who has spent many many hours near birds in the air, most that are not in that category, upon seeing you come at them (if that is the case and time allows) instinctively fold their wings and drop. That's their form of collision avoidance.
OP, sorry for your loss, I feel your pain. Take solace that you flew safely, and were over nothing when it happened, (Unless we get reports of tragic fish injury).