The heartwarming reason this dog made a mother cry

For some, dogs are more than a fun companion: they can have a calming effect during tough times. One mother realized that for her autistic son, and the result is moving.

On the Love What Matters Facebook page, a person named S. Niehaus submitted a photo of her, her son and her son's new service dog, Tornado:

"See this moment? I've never experienced a moment like this," the mother began. She went on to discuss that this was the first time her son met Tornado.

RELATED: Look and these adorable, happy animals

"We are Americans that live overseas in Japan and have prepared for nearly two years to meet Tornado," she said. Tornado is a service dog from the non-profit organization 4 Paws for Ability, which provides service pets with children worldwide.

She explained the pain she and her son feel because he hasn't been able to make a connection with people outside their family. Now, her son has clearly made a bond with Tornado.

"As a mother, I have seen countless challenging and painful moments my son has encountered and cried countless more," she said. "Yesterday however, I cried for a different reason. It is a feeling that is indescribable."

S. Niehaus' story has touched many people: the post has been liked and shared hundreds and thousands of times.