We had that here in Cambridge on the towpath along the River Cam- possibly targeting rowing coaches, but it would also have harmed commuters and especially dogs.
Fortunately if it’s just tacks, there’s a relatively easy way to remove them:
Hopefully whoever is behind this sort of thing is less competent than the professionals. The fact that detection and collection of metallic, especially ferromagnetic, objects is a comparatively well behaved problem is why minimum-metal mines were developed in relatively short order.
At least in media depictions; the answer usually seems to be ‘be a nurse whose work is surrounded by a suspiciously(but not enough to be followed up on for quite some time) elevated patient mortality rate’.
Aside from that, though, it doesn’t seem to be an equal-opportunity field by any means.
According to the article, the LEOs released the K9 on the fleeing teens (robbery suspects) but then an officer got in between the dog and the suspect so he got mauled by the dog and in response he shot the dog.