(NewsNation) — Two children were burned after vandals poured acid on a park playground in Massachusetts. The mother of the children said that although she wasn’t initially concerned about how the acid got there, she wants the person responsible to be held accountable.

“It was probably just some kid or some teenager that, you know, kids that age, they’re not thinking about what’s going to happen next,” Ashley Thielen said. “But who knows, that could have been some sick person that … has a premeditated plan to go do this, to try to hurt kids. Which is even more disturbing if that was the case.”

Thielen joined “NewsNation Now” to share her story of what happened the day her children came into contact with the acid.

She said her 1-year-old began crying after he sat down at the base of the slide, but she didn’t realize the severity of the situation until the jacket where she was holding him began to tear apart.

“That was the first thing that sort of tipped me off that this wasn’t just water. And also, right at that moment, my daughter started crying and saying, “Mommy, it hurts, it hurts.” And she was pointing at the back of her leg,” Thielen said.

By the time Thielen was able to get her kids home, she said her daughter’s skin “was already starting to kind of bubble up on the back of her leg.”

Authorities believe someone broke into a nearby pool facility and stole hydrochloric acid from the basement pump room. The suspects got into the pool room through the ventilation shaft, investigators said.

Hydrochloric acid can cause severe burns when it comes in contact with skin, and its vapors can even be dangerous to inhale.

“As time went on, I started to get more and more angry and just upset about how bad it could have turned out,” Thielen said. “We got really lucky.”