Since 2007, over a dozen severed feet still inside their shoes have washed up on the beaches of the Pacific Northwest. Here are some possible answers to this grisly mystery.

Over the past decade, 14 severed human feet still inside their shoes have found been along the shores of the Pacific Northwest near Washington and British Columbia. There have been some men, some women, and various ages and sizes. The facts can get more specific than that if you want them to (more men than women, some Nikes and lots of New Balances), but it doesn’t change the fact that that’s effectively all we know.

And now we have another foot to add to the pile.

On the afternoon of May 6, 2018, the most recent foot was discovered. A man was walking along a British Columbia beach when he found the foot lodged in a pile of wood on Gabriola Island. This foot was in a hiking boot, which is a unique detail given that all but one of the other feet found thus far were in athletic sneakers. But that’s essentially all the information authorities will disclose.

Once again, the remaining facts — the little that there are — won’t provide much help in answering the big questions: Where did these feet come from and why are they severed in the first place?

The proposed explanations, some coming from law enforcement and some coming from amateur sleuths, are as varied in both content and quality as you’d expect. Some suggest we’re finally seeing the remains of victims who went down in a nearby plane crash in 2005. Others suggest we’re seeing victims of the 2004 Asian tsunami, their bodies pulled northwards over the course of ten-plus years by the strong Pacific current. Others still suggest, of course, a serial killer.

While law enforcement agrees that the frequency with which these feet are appearing is astonishing and unprecedented, they generally suggest a far more basic answer: suicides and accidents. Two of the feet belonged to people with mental illnesses and three belonged to people who are strongly believed to have died of natural causes. Across all the cases, foul play is generally not suspected, according to the British Columbia Coroners Service. And all involved are quick to point out that ocean currents, over time, can easily cause a limb to detach from a decaying body.

Still — given the frequency, the commonalities in footwear, and more — some suggest that there are just too many coincidences for this not to be something deeper and darker. And you certainly can’t blame them.

For more extraordinary head-scratchers, check out these mysteries of ancient history and the five greatest mysteries in human history.