It’s always heartbreaking when someone abandons animals, but some people do it in especially cruel ways that leave the animals’ lives at risk. That was the case recently, when a litter of kittens were left in a cardboard box with no air holes ?

Employees at the Pasadena Humane Society, in California, arrived to a heartbreaking surprise on October 29. They heard a “faint meowing noise” coming from their Animal Resource Center, and soon discovered a cardboard box — filled with seven tiny kittens.

The box was taped-up shut and had no air holes. The person who left them labeled the box “Kittens.” Thankfully, all 7 kittens were alive and unharmed, but they were shocked and saddened that anyone would have such a reckless disregard for the cats’ lives.

“While we’re relieved that these little ones were uninjured, this is a crucial reminder that abandoning animals in unsafe conditions can put their lives at serious risk,” Pasadena Humane wrote in a Facebook post. “If you are unable to care for an animal, please reach out to us so we can assist you further.”

The kittens were taken in by the shelter. Many people commented on the post, expressing heartbreak that the cats were abandoned like this and thanking the humane society for caring for them.