The first card was postmarked Hartford, Conn. I assumed it was sent by a reader from my old paper who was nice enough to follow my work when I moved to Philly, and even nicer for hand-writing a note of appreciation.

But then a day or so later I got a batch of similar postcards. And the next day, another. And then I was sure I had missed something.

I noticed the words Postcard Underground written or rubber-stamped on several of the cards.

Postcard what?

A Google search turned up some clues –— mostly a handful of stories by people who were just as humbled then stumped as I was by the cards’ mysterious arrival. The authors sometimes signed their first name, maybe a last initial, but offered few other clues to the coordinated random acts of handwritten kindness sent to people and causes they find inspiring. Such as:

A faculty member at Montana State University Billings with the courage to speak publicly about her Muslim faith. A Minnesota nonprofit for people who have lost limbs. A retired Minnesota Public Radio reporter whose colleagues tracked down the postcards’ mastermind to a Sue from Minnesota — or so they thought.

Clearly, there’s a Minnesota nice connection. But the cards are postmarked from all over the country, including California and Seattle and Denver and Boston, which, as a Boston University graduate, I can attest isn’t exactly known for being wicked friendly.

The cards that suddenly appeared in my office mailbox lauded my attention to gun violence, including a story about the lasting challenges faced by gunshot victims who survive that I wrote with David Gambacorta.

“Your work on gun issues is important and appreciated,” read one card. Some renamed me Helen Gubinas, but this was coming from a good place, so no hard feelings.

Like those before me, I tried to figure out how the writers connect and communicate. I noticed one sender from Minneapolis had included, inadvertently I think, her first and last name. I won’t out the kind writer, but her name was unique enough to turn me into a detective for about a week, leaving messages for at least half a dozen Minnesotans who are probably wondering just what’s in the Philadelphia water. (If I did stumble on the right person, I’d love to hear from you. Maybe you’d consider letting me join the group — because who doesn’t want to be part of a secret society of kindness that cuts through the noise, especially when these days noise seems to be the country’s official language.)

I think that’s why another piece of correspondence, tucked between the second batch of postcards, left such an impression.

This time, it was a thick envelope. More postcards, I thought. But when I opened it, I saw that it was handwritten cards from Philadelphia students, intended for a man I had written about a couple of months ago.

In November, Luis Berrios was shot in the back during an attempted robbery. While still lying in his hospital bed, he drafted a letter forgiving the people who shot him.

The students from Liguori Academy, a private, independent high school in Kensington, were floored, their English teacher Carolyn Bjornson later told me. And like the Postcard Underground, they were inspired to write him.

Mia Rettberg, a sophomore, said that like most of us, she usually communicates through texts and emails and various other electronic platforms that promise to keep us connected but seem to have the opposite effect. Writing the letters by hand forced her to choose her words more carefully, she said.

“It seemed a lot more serious.”

The letters were all great, but a line in one of them stood out for me.

“I want you to know that you are being heard,” wrote Katie Brown.

A simple declaration that perfectly sums up why those postcards make such an impact. And why Berrios was so touched when I sent him a text — the irony of that wasn’t lost on me — with a photo of all the letters. These days it’s nothing short of miraculous when someone or something cuts through the noise to tell you that you are seen, and heard.

Berrios was back in the hospital with some complications from his gunshot wound, but was buoyed by the cards I promised to bring to him.

“Them cards!” he texted back.

Them cards, indeed.