A California family was left 'heartbroken' after shocking security footage showed their postman routinely dousing their rescue dog with pepper spray.

Owner Alfonso Galindo installed security cameras on the exterior of his San Diego home after he was left baffled by strange stain pattern that kept emerging on the ground of his front-yard for months.

However, the father-of-two was left 'heartbroken' when he reviewed footage from last Tuesday and saw his family's beloved seven-year-old rescue dog, Pupa, writhing around in pain as a postman approaches his San Diego home.

On closer inspection, Galindo noticed the postman appeared to spray something from a canister at the poodle-mix's face, as he barks excitably from behind a secure gate.

Pupa is first seen barking excitably at the gate, as the postman approaches the San Diego home

Suddenly Pupa turns away and begins rubbing her face on the ground

The seven-year-old rescue writhes around on the floor for several moments, clearly in a great deal of pain

Alfonso Galindo (left) says the footage left him absolutely heartbroken, calling the postman's actions 'criminal' and a breach of trust

Inspecting the footage from multiple angles, Galindo spotted the postman carrying a canister in his hand, believed to be pepper-spray

A helpless Pupa then turns away and begins desperately rubbing her face into the pavement.

Galindo said he reviewed security footage from the past month and found at least nine other incidents where pupa 'convulses in some sort of ritual pain' as the postman passes the gate.

'Never did I suspect the mailman. Never did I suspect somebody that you trust with your mail, with your packages,' Galindo said to KNSD. 'It was heartbreaking, it was really heartbreaking.'

'I'm at a loss for words,' he added. 'It makes me sick to my stomach.'

In hindsight, Galindo said he noticed on a number of occasions that Pupa had blood-shot eyes but it always went away soon after.

He also says that his two children, Alfonso Jr., three, and Regina, one - who both regularly interact with Pupa - have both developed serious respiratory issues in the last six-months, which he now believes has been triggered by chemicals from the pepper spray in the dog's fur.

'I get livid thinking about it. This is the health of my children' Galindo told WDSU. 'I believe what he's done to my family is criminal.'

Galindo first grew suspicious something strange was happening at the home when he noticed a stain pattern emerging on the floor of his driveway - he said he never expected the postman

As a result of the chemicals on Pupa's fur, Galindo said both of his children - Alfonso Jr. (left), three, and Regina (right), one - have developed serious respiratory issues over the past six months, as they regularly interact with the dog

After Galindo complained to USPS last week, the delivery company issued a statement on Tuesday following an internal investigation.

'On behalf of the United States Postal Service, we want to apologize to the Galindo family and Pupa,' the statement read.

'We do not condone our employees behaving in a manner which is not professional and courteous. The appropriate personnel and corrective action will be taken as well as training given to all local letter carriers.'

The postman in question hasn't been named. It's not yet clear if he will face any charges in relation to the attacks.

San Diego police have asked anyone in the area who believes their dog may have also been pepper-sprayed to call them on (619)-531-2000.