In the black depths of the deep sea, scientists have captured rare footage of two person-sized squid with giant flashing lights at the ends of their arms.

The animals, both of the species Taningia danae, approached and latched onto a remotely operated vehicle scientists were using in a part of the Pacific Ocean that had never been explored before.

“The remarkable thing about these observations was that both squid were aggressive toward the ROV,” said Michael Vecchione, a squid expert with the National Oceanic and Atmospheric Administration at the National Museum of Natural History.

Most deep-sea octopi and squid don’t seem to respond to the bright lights of deep-diving submersibles, he said, but these two appeared drawn to them. And that might support a theory on why other deep-sea creatures light up in a region of the ocean that sunlight doesn’t touch. The hypothesis, called burglar-alarm bioluminescence, is that jellyfish and other prey animals light up when attacked in the hope of attracting even larger predators (like the squid) to eat whatever is bothering them.

As for the squid, they demonstrate other uses for bioluminescence. Their light-emitting organs, called photophores, are the largest we know of. They flash unusually brightly, more like strobe lights than the gentle glow of most other bioluminescent animals. Scientists think they use those flashes to startle predators or momentarily stun prey.

The deep sea has barely been explored, and it’s particularly rare to catch its mobile residents like squid on camera in their natural habitat. Scientists will continue to study the latest footage to learn more about these mysterious deep sea predators.