Lisa Gafkjen’s son, Tayder, just turned 19 and is in basic training for the North Dakota Army National Guard. She and her family have been waiting for letters from him, and what a window clerk at a post office did to make sure his letters made it home left her emotional.

Lisa posted the photo below of an envelope full of letters she received from Tayder, covered in writing. She said when she looked at the envelope, she noticed her son’s handwriting — then someone else’s.

“I read his part first and it said he hadn’t gone to the store yet when I talked to him last,” she said.

Then, when she kept reading, she saw the words: “Pd. by window clerk” and an arrow pointing to words that said, “Thank you for protecting my freedom.”

The postal worker saw that Tayder, who was running low on stamps and hadn’t been able to go to the store, didn’t have enough postage on his mail. That’s when the worker wrote the messages on the envelope, and paid the extra $3.67 so the letters could make it home to his family.

“It was pretty emotional,” Lisa said when she realized how the letters made it home. “I was fighting back the tears, the postal worker paid his postage. It was really special.”

She said she would love to one day be able to thank this postal worker herself, and that she wants them to know their kindness meant the world to her and her family.