What to do about someone throwing ham-wrapped laxatives into my garden?

But if a strange one, any opinions or advice gratefully received.

Context: We live on a street of terraced/semi detached houses. Alley runs along the back to enable rear access to gardens/garages etc. Have one dog, he’ll run to the back fence and bark if people are making noise in the alley (it’s a nox hotspot at times) but he’s not excessive and is never left outside alone for any period.

On Sunday morning I was near the back of the garden and something caught my eye on the ground. A small package, wrapped in cling film with a band of tape round the middle and a foil “cap”. As I picked it up the foil came off and a bunch of dog treats fell into my hand. Looking closer, the package contained a slice of ham wrapped around half a dozen or so dog treats. And 3 laxative suppositories.

So clearly someone is trying to get at us via the dog. Fortunately he’s very well trained, so he doesn’t eat food from the floor. He’s also previously found a box of laxatives at my dad’s house and was totally disinterested.

So good people of Reddit- why’s someone trying to poison my dog, and what do I do about it??!