What began as a typical puppy playdate between 3 dogs turned deadly this weekend after an encounter with blue-green algae.

Melissa Martin, one of the dogs’ owners, said that she took the dogs to a local pond in Wilmington, North Carolina, and were having an amazing evening playing in the water. It wasn’t until the dogs started showing severe symptoms that Martin considered they may have contracted something.

The dog owners rushed their pets to a nearby vet where they were told their dogs had ingested a lethal amount of toxic blue-green algae. The three beloved pets were declared dead around midnight.

“They contracted blue-green algae poisoning and there was nothing they could do. We are gutted,” explained Martin in a Facebook Post.

According to Alberta Health Services, ingestion of blue-green algae may lead to skin irritation, rash, sore throat, sore red eyes, swollen lips, fever, nausea and vomiting and/or diarrhea. They say that symptoms come on quickly and usually resolve within a few days, but children often have more pronounced and serious symptoms.

For animals, it can be even worse.

According to Pet Poison Helpline, ingestion of blue-green algae for dogs can lead to any of the following: vomiting; diarrhea; blood in stool or black, tarry stool; pale mucous membranes; jaundice; seizures; disorientation; coma; shock; excessive secretions (e.g., salivation, lacrimation, etc.); neurologic signs (including muscle tremors, muscle rigidity, paralysis, etc.); blue discoloration of the skin and mucous membranes; difficulty breathing; and death.

“I wish I could do today over,” Martin continues. “I would give anything to have one more day with them. Harpo and I had work to do, but now we will carry on in his memory and we will make sure every standing body of water has a warning sign.”

Martin has since started a GoFundMe to spread awareness about the harmful effects of blue-green algae and how to spot it to prevent more needless dog deaths.