A letter left at the scene claimed that the dog barks 'too much', and therefore must be 'poisoned'.
Sixty-six-year-old Cheri Blair, from North Sydney, made the horrific discovery near to her home at around 6.00am on Monday morning.
She immediately rushed her Portuguese Podengo Jolene off to seek medical assistance, and she had to remain at the veterinary centre all day.
It all started when the dog failed to return to Cheri in the garden as usual, and upon searching, she discovered that Jolene had found a bone around the corner.
Speaking to The Daily Mail, she said: "It was one of those ones that you have to go to the pet store to get there, like a freeze-dried bone, quite big."
Cheri said that she initially chucked the bone over the fence and thought little more of it, but then she found the terrifying letter.
She continued: "Something made me go down there [again], and then I looked down. There was a letter, but it was sealed in an envelope and it had the message on it."
The note read: "Your dog is to be poisoned, to [sic] much barking, sorry but no choice, your falt [sic]."
Blair said: "'I just started freaking out and I started screaming at my husband, 'Go get the bone!'
"They couldn't even spell, it was horrible."
She rushed Jolene off to the North Shore Veterinary Hospital, where the doctors induced vomiting.
She explained: "We don't know for sure [the bone was poisoned], but I was going to take any chances. I mean it's obviously quite threatening."
The day before the incident occurred, Ms Blair said that Jolene had barked for around 20 minutes with two other dogs.
Later that evening, Jolene barked again and Ms Blair said she heard a female voice shout 'shut up' from the 60-unit apartment block near to her house.
Blair bought Jolene over Christmas after her previous dog died of cancer, but has no idea who is responsible for this attack.
She said: "There's only one person I've had an issue with throughout the years. I don't think it was him because he's now got himself a Covid dog but he used to hate dogs.
"I'm here all the time, she doesn't bark at night at all."
New South Wales Police have inspected the back garden for DNA testing, and have contacted the people living in the apartment block.
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