In July 2019 a game warden in Bridgton, Maine, got an unusual call: A bald eagle was floating lifeless in a lake. At the time, biologists suspected the animal might have been shot or poisoned by lead fishing tackle—all too common causes of death for wild birds.

Now, tests have revealed the bird’s bizarre demise: A stab wound directly to the heart. The murder weapon? The dagger-like beak of a common loon. (See a photo of the dead eagle.)

It’s the first time a loon killing an eagle has ever been documented, says Danielle D'Auria, a wildlife biologist with the Maine Department of Inland Fisheries and Wildlife.

According to D’Auria, a dead loon chick was found nearby,