According to News.com.au, Kelly Lacey, who works as a bird coordinator for the New South Wales Wildlife Information, Rescue and Education Service (WIRES), has been looking after populations of birds she suspected were poisoned from eating mouse bait.

On Monday, she reportedly went to check on a flock of approximately 100 galahs in a Parkes, New South Wales cemetery—but what she discovered was a horrifying scene, in which all but two birds were found dead.

Lacey shared photos of the birds on Facebook, writing that it was a “[scene]…that finally broke [her].” She wrote that “this beautiful flock of Galahs…[lived] in and around the cemetery,” and noted she had rescued and cared for injured flock members in the past. “Seeing them sitting with each other under trees, knowing they were suffering until they have eventually died, has utterly broke me.”

In her post, Lacey added that of the two live galahs she salvaged from the flock, one died in the car ride home. She also clarified that while she does support reducing the vast mice population, she does not condone the use of “poisoned grain” that might harm other species.

Lacey expanded on her thoughts in a statement to the Australian Broadcasting Corporation (ABC News): “Seeing the dead bodies and picking them up was just truly heartbreaking.” She also said she saw blood in the birds’ feces, leading her to suspect that the poison caused internal bleeding.

Meanwhile, the NSW Environmental Protection Agency (EPA) has verified that numerous cases of recent bird deaths can be traced back to poisonous mouse bait, says News.com.au. In response, the EPA’s Executive Director of Regulatory Operations Carmen Dwyer cautioned people to be extra careful when using these types of poisons.

“The safe baiting of mice is an important step in reducing mice numbers,” explained Dwyer, “and pesticide users must make sure they handle baits safely and are careful to always follow the directions on the label to protect their family, [neighbors], domestic animals, wildlife and the environment from harm.”

She added, “Our advice is to think carefully about where the bait is being placed, only use the recommended amount of bait.”

Australia’s mouse plague is wreaking havoc on the nation, disrupting everything from the food supply chain to individuals’ daily lives. Last week, for example, it was reported Australian farmers are facing a potential $775 million loss due to mice invading and overrunning their fields. Only days prior, a family in rural NSW lost everything after mice chewed through their home’s electrical wiring, sparking a massive fire.