Work crews made the gruesome discovery of 4,000 human bones from the Civil War era at Fort Mason Back in 2010. Now researchers think they’ve found the culprit behind them, a famed 1870s doctor who specialized in amputations.

Some interesting Fort Mason history: It wasn’t always called Fort Mason. Before it became a popular gathering place for outdoor movies and food truck meet-ups, it was originally constructed as an Army post called Point San Jose in 1863.

And we should note that the Army post had a hopital. Which might explain some more interesting and far more grisly Fort Mason history: Back in 2010, National Park Service workers discovered more than 4,000 human bones during a dig there while cleaning up contaminated soil (and the week before Halloween at that!).

They also found pill bottles and hair tonic from the 1870s, among the thousands of bones and bone fragments, which were all different people’s bones chopped up and mixed together. Many of the bones had saw marks on them, and some of the human skulls were even split in half.

There were no medical records found, nor any explanation or context discovered with the bones. So forensic anthropologists from Cal State Chico have been on the case since then, and they may have cracked the case that the discarded bones were the doing of a Dr. Edwin Bentley.

The researchers made that case in their recent exhaustively researched book Archaeology and Bioarchaeology of Anatomical Dissection at a Nineteenth-Century Army Hospital in San Francisco. That’s obviously an academic title, so the Chronicle breaks down the case of how Dr. Edwin Bentley is probably responsible for the thousands of severed human bones from the 1870s.

Dr. Bentley was not some Jack the Ripper type; he was a doctor famed for his skill at amputations. That procedure was much in demand during the Civil War, and “The success rate was not high at all,” one of the book’s co-authors, Golden Gate National Recreation Area archeologist Peter Gavette, told the Chronicle. Bentley was a teacher at the Army base hospital when he arrived here in 1869, then taught anatomy at University of the Pacific Medical College for five years, and also performed autopsies for the city at the SF City and County Hospital.

Bentley was “quite the famous surgeon and anatomist, and he also had a penchant for disposing of remains in unusual places,” another co-author and Cal State Chico anthropologist Eric Bartelink said to the Chron. “Of course, today we look back on this and realize it does not remotely mesh with current-day ethics.”

The researchers determined that the bones belonged to 25 different people, with no complete skeletons in the bunch. Forensics showed these people were impoverished. And the law at the time said that if no family members claimed a dead body within 24 hours, the bodies could be used for medical research and teaching. Given that this was the Gold Rush era when most San Franciscans were transplants, many bodies were not claimed during that period.

So, Bentley simply used the dead bodies of poor people to teach anatomy and surgery classes. The researchers dug up a speech where Bentley himself said, “The supply of ‘subjects’ was ample for all the requisite needs of the professors and students.” And this was actually quite progressive at the time, as grave robbing was fairly common at medical schools of the era.

And the researchers are still working on piecing together more stories about the people whose bone remains were found at Fort Mason. “We’re giving a voice to people who were voiceless when they lived,” Bartelink explained to the Chronicle. “Society didn’t seem to care for them. But this research gives us a window to tell their stories.”

The bones remain at Cal State Chico, though they are the property of the National Park Service. The researchers will continue to see what they can dig up about these people whose bones were found buried underground.

Related: Mysterious Human Bones, Hair Tonic From the 1800s Found Near Fort Mason [SFist]

Image: National Park Service