The RSPCA is investigating the poisoning of two dogs at a Singleton home on Monday morning.
Justin Wishart had returned to his Eucalypt Close home from a morning trip to Bunnings about 10.30am when he noticed his eight-year-old staffy-heeler cross Diesel was unwell.
The family's two-year-old Jack Russell-Maltese cross Ratchet was also in distress.
"Ratchet was in a bad way, shaking, he was having trouble breathing, he was drowning on his own phlegm," Mr Wishart said.
"My eldest son Tyler and me just sat with the dogs, rubbing their tummies."
The diesel mechanic discovered hundreds of small blue pellets, believed to be snail bait, littered along his side fence.
Mr Wishart said he was able to scoop up enough pellets to fill a plastic shopping bag.
After a panicked call to his partner Kristy Shimkus, the couple rushed to a Port Kennedy vet, who told them little could be done to save their beloved dogs.
"The vet said they had ingested a lot of poison," he said.
"They pretty much suggested Ratchet was going to die and Diesel pretty much was going to be the same.
"There were no guarantees.
"So we made the heartbreaking decision to put them down."
Mr Wishart, Ms Shimkus and their four children said they had been left devastated by the poisoning and could not comprehend why their dogs were targeted.
"Last night, I had two girls in the bed bawling their eyes out and Tyler, my eldest, took it the hardest because he was home and saw it all," Mr Wishart said.
"We'd washed up all the spew and everything. The dogs were buried by the time the other kids got home.
"It was quite a shock. I'm not really too sure why anyone would want to do that. There had been a fair few tears, woke up again this morning in tears and we've had a talk about the dogs and now they've just got good memories."
Mr Wishart said he hoped the perpetrator would be caught and urged anyone who saw what happened to come forward to authorities.
RSPCA spokesman Tim Mayne said he was sickened to hear about the incident and asked for anyone who saw any suspicious behaviour around the Eucalypt Close property on Sunday or Monday to contact the RSPCA on 92099300 or 1300 278 358.
Witnesses can also report any animal cruelty online at www.rspca.org.au .
Anyone found guilty of intentionally or recklessly poisoning an animal can face a maximum penalty of five years imprisonment and a $50,000 fine.