East Bay dog owners are on alert this week, after thousands of thumbtacks were found scattered throughout a Hercules dog park. Police were called to Ohlone Dog Park on Saturday after park-goers reported finding the metal spikes earlier that day and Friday.

At least one regular told KRON 4 News that they first noticed the tacks in January, and since then have discovered many more. And those who spend time at the park are not just concerned about their pets (which they are definitely concerned about), but are also worried about children at the nearby Ohlone Elementary School.

"Anyone that would have the heart to do something like that, I don't know what they'd be up to next," one dog owner, Larry, told the channel. "And it's sad to think that there's people out there that actually do these type of things."

Larry, who did not give his last name, said he even discovered roughly 500 tacks in the stream adjacent to the park.

This case calls to mind the numerous incidents of meatball poisoning that struck San Francisco over the past few years, wherein some twisted individual (or individuals) was intentionally leaving meatballs filled with poison around city parks popular with dogs. At least three dogs are believed to have become ill after consuming the poison meat. In the summer of 2013, poison-filled meatballs were found in the Lower Haight, Cole Valley, Hayes Valley and Bernal Heights.

No culprit was ever determined in the poison case.

With reports that at least one Hercules dog has swallowed a tack, police are taking this past weekend's incident seriously and are asking anyone with information to call 510-799-8260.

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