His cousins from Ireland were in town and the 6-year-old had spent a hectic few days visiting Niagara Falls and local water parks, says Jennifer Crowley.
"I said to him, 'Padraig, why aren't you eating your lunch?' " Crowley, 41, of Scottsville, New York, tells PEOPLE.
"He said, 'My stomach hurts,' " she says. "Then he'd go play with his cousins."
Though she'd had a son, Cian, who had died of neuroblastoma, a rare childhood cancer that often starts in the abdominal area, doctors had assured her the chances of having another child with it were "the same as anyone else's" because he did not have the genetic form of the cancer, she says.
She'd worried for years the three children she later had (Eloise, 2½, Padraig, whose nickname is Paudie, and Noel, 4) would get it – and had made sure they were rigorously tested for the disease at young ages – but gradually those fears had faded away.
"I started to think we were getting away from it as a real possibility," says Crowley, vice president of marketing for a health information software company. "The doctors did the screenings to give me peace of mind."
So she and her husband, John, 42, a carpenter, weren't worried about Padraig.
But by Saturday morning, when he still wasn't eating – and a trip to his pediatrician the day before hadn't offered any answers – it was clear something was very wrong. They went straight to the emergency room.
"His blood tests showed some abnormal numbers," says a weary-sounding Crowley. "We told them we had a son who'd died of neuroblastoma, so they did an abdominal ultrasound."
And this is how their world turned upside down.
"Within three hours, we had a diagnosis," she says. "He had a primary tumor on his adrenal gland with bone marrow involvement. It was neuroblastoma, stage IV. High risk."
"I really thought I was dreaming," she says. "I always thought this was an irrational fear I had. And the fact it was happening again. I still don't know if I've internalized it."
This time, though, something amazing happened.
After Crowley started a Facebook page to keep everyone updated, word of Padraig's diagnosis spread rapidly around the community, which quickly jumped in to help.
One friend started a page on which people could sign up to help with chores, errands and meals.
Another started a fundraising site to help pay for medical bills and other expenses.
"It's going to be a long haul," Tim Limner, 42, a freelance filmmaker who started the site, tells PEOPLE.
"I just felt like if we could just say, 'Here's money,' then they could get what they need," he says.
Padraig faces months of chemotherapy and a lengthy hospital stay at Memorial Sloan Kettering Cancer Center in New York City, so it's unclear how much help they'll need, Limner says, which is why he keeps bumping up the fundraising goal.
Fundraising Events This SaturdayIn addition, there are a slew of fundraising events at this Saturday's Scottsville Family Fun Fest, including a dunk tank, a head-shaving station and "Team Paudie" T-shirt sales.
Crowley, who's only lived in the town for three years and didn't know that many people, was blown away by their generosity.
"We're so grateful because we've been through this once and it was one of the most isolating experiences," she says. "This time it's like we have this whole team fighting for us."
After Cian's death, Crowley formed Cian's Cause to raise awareness about neuroblastoma, symptoms of which can include "raccoon eyes" and fractured clavicle bones at later stages.
"The doctors just went right into the diagnosis of child abuse," she says. "It was horrible."
Cian eventually got the right diagnosis, but he died five weeks later. Not long afterward, Crowley was pregnant with Padraig, who "picked us up out of the darkness," she says.
"He saved us," she says, "and now we have to save him. And that's all there is to it."
And, this time, she has "Team Paudie" there to help.