Durham police are investigating a disturbing case of dog poisoning that has cost a beloved pet its life, and sickened another dog owned by the same devastated family.

Zoe a 3-year-old Boston Terrier died after ingesting what a vet believes could be antifreeze.  The family's other dog Riley also suddenly fell sick after the two dogs went for a walk in a Parkette in Whitby.

"It's ripped my family apart the last couple of days...watching that dog slowly die for two days is the hardest thing. She would look up at you with her big brown eyes going, 'why isn't there anything you can do to help me?' " said Jennifer Dennis. 

"To know that that dog suffered and she didn't have to (is heartbreaking)," she adds through tears.

Jennifer's mother took both dogs out for about 20 minutes. They ran through a local ravine and also spent some time in Iona Parkette.  When they got home later on that evening they became very sick.

The Parkette has been scoured twice by animal control officers who didn't find any clues as to what could have poisoned them.

Earlier this week three dogs fell sick after eating what police believe were contaminated cupcakes left in a Port Perry park.