Onlookers may not be responsible after all for the death of a moose this weekend in Lake Champlain.

The story drew outrage on social media after officials suggested people crowding the shores to take photos scared the tired moose back into the water where it drowned.

Tuesday, Vermont moose biologist Cedric Alexander said brain worm parasites probably killed the animal. He said moose with brain worms are often disoriented and can't coordinate their body movements. Alexander said exhaustion might have played a role but the animal's actions pointed to brain damage, saying, "There's no way it's just going to swim out and drown unless it's being chased by a power boat."