In an unprecedented event, researchers have documented the first known instance of a shark being eaten by a larger predator in the open ocean.

The incident involved a female porbeagle shark southwest of Bermuda, which not only lost her life but also the lives of her developing pups. Detailed in the journal Frontiers in Marine Science on Tuesday, the study sheds light on a rare predatory behavior.

“The data presented in this study is, to the best of our knowledge, the first evidence of predation on a porbeagle and provides novel insight into inter-specific interactions for this large, globally vulnerable shark species,” the study states.

Researchers tagged a 7-foot pregnant porbeagle shark near Cape Cod, Massachusetts, in October 2020. They attached two tracking devices to her — one on her dorsal fin to transmit location data and a pop-up satellite archival tag to record temperature and depth.

Although the PSAT was designed to detach after about a year, it unexpectedly popped off after five months, near Bermuda. “The predation of one of our pregnant porbeagles was an unexpected discovery,” a study co-author, Brooke Anderson, said, Fox News reported.

Porbeagle sharks, which populate the Atlantic, the South Pacific, and the Mediterranean, can grow up to 13 feet long and weigh as much as 500 pounds. The data from the PSAT showed erratic diving patterns and increased temperature readings just before detachment, indicating that the tag had spent several days inside another animal’s stomach.

Researchers ruled out mammals like orcas, due to their warmer internal temperatures, and focused on endothermic sharks instead. The study suggests that the pregnant shark may have fallen prey to one of the ocean’s apex predators. Only two species are large enough to have consumed a 7-foot porbeagle — the white shark and the shortfin mako.