An anonymous tenant has left a graphic letter in more than 150 mailboxes threatening violence against a barking dog and its owner.

The furious neighbour contacted all residents at the Alto Apartment in the Brisbane suburb of Toowong, saying they believed the dog was being mistreated based on its incessant barking.

The letter, obtained by news.com.au, initially starts with 25 lines repeating the word 'bark', before the author launches into an expletive-laden tirade against the dog's owner by translating the barks.

'This roughly translates to 1) Help I am in prison! 2) My owner is a f**kwit 3) I want to jump off this building and die,' the letter reads.

The furious neighbour contacted all residents at the Alto Apartment (pictured) in the Brisbane suburb of Toowong, stating they believed the dog was being mistreated based on its incessant barking

'I would love to lock you on a balcony for hours on end, with or without food and water for weeks on end and see how you cope,' it said.

The author of the note went on to tell the dog's owner they had already contacted the local council, but had thought ahead in case the council would not act on the complaint.

'I will contact channel 7… 9… 10… human rights… animal rights… PETA…'

The author also says they will hire lawyers or QCs to 'stop this evil act from occurring.'

'If council are soft c**ks and can't solve the problem I will go to police.'

The neighbour went on to write in bold font: 'I will bring you down.'

'You must not (have) been loved enough as a child or f***ed enough as an adult,' they wrote.

The author of the note went on to tell the dog's owner they had already contacted the local council, but had thought ahead in case the council would not act on the complaint (stock)

'You are truly a sick twisted individual and should not be allowed to own pets. You are everything that's wrong in this world.'

Despite the author trying to point out the owner's so-called abuse, they then threatened to 'scale the building and throw the dog off'.

'Not onto the train tracks... but into the drive way area so other tenants could see the dog is free from a painful life of abuse'.

The furious tenant who penned the letter goes on to assume the owner of the dog is a 'poorer tenant from floors 4 to 10'

'But who knows a lot of rich people are stupid and can't even tie their shoelaces, that's why they are reading this too. Rich wa**er.'

The letter finishes with yet another threat, 'At the end of the day I won't be the one in the mental asylum or jail having their a****le played with. You will be.'

Terrified tenants have expressed concerns over the anonymous neighbour's rage.

Some said they had never even heard a dog barking in the building.

Alto Apartment’s management is allegedly investigating the incident.