The Monster from Earth's End — Murray Leinster

There was nothing on the island big enough to kill a man, yet each new day brought with it another bloody death, another mysterious disappearance.

The first hint of something wrong at the outpost was the plane. It crazily circled the little island, its cargo-bay doors open, its radio dead. It seemed to hang in the air for a moment and then it dived downward, levelled and dipped again. It made a belly landing on the runway with its wheels still retracted.

There was a singular, dead silence and then a shot rang out.

The crew of two and the seven passengers had vanished, the cargo was strewn about and the fuel tanks had been emptied. And the pilot, after landing, had blown his brains out...