SAN JOAQUIN COUNTY (CBS13) — The San Joaquin County Sheriff announced a gruesome discovery that could be tied to a serial killer nightmare that ravaged the county just a few decades ago.

A bone found in a well by a local farmer is eerily similar to human remains found a few years ago that was tied to the Speed Freak Killer case, the sheriff’s office said.

“We do not know — I’m gonna say this over and over again — whether this is an animal bone or a human bone,” Sheriff Patrick Withrow said in a press conference on Thursday.

To understand why a sheriff’s focus on a single bone is causing such a stir, we need to remind you of the crimes of Wesley Shermantine and Loren Herzog.

The Speed Freak Killers — two buddies convicted of four murders in San Joaquin County — were given that name because of their drug-fueled crime spree. And it’s believed they killed a lot more.

Shermantine swears by it, even drawing up maps showing investigators where to go to find more remains. In 2012, investigators did and discovered human bones deep in a well.

This latest find is strikingly familiar. The farmer’s discovery within the past month is now leading to Withrow reminding victims’ families of his promise — to not let this case go.

“I reached out to as many family members as we could who have been victimized by the speed freak killers in the past,” the sheriff said.

Those families have been frustrated, alleging the previous administration dropped the ball in helping to identify their loved ones. The sheriff says his department is ready to finally unearth some closure, even if it takes one bone at a time.

“We’re not going to quit until we find out and get the answers,” Withrow said in the press conference.

For now, investigators have not reached out to Wesley Shermantine. If the bone is found to be human and a DNA connection is made, they likely will reach out to see if he can lead them to other remains.