A new commercial has been spreading around the internet, and its ending is a serious punch to the gut.

At the beginning, we meet Evan, a high school kid who can’t wait for summer break. He’s so bored that he begins etching words into a table in the library. The next day, he finds that someone has written back to him on the table, and there ensues a back-and-forth that’s pretty captivating.

There seems to be romance building, or at least the hint of it. Who’s been writing back to Evan? And will he ever connect with them?

But at the end, you learn that there was something else going on while we are watching this burgeoning love story. Can you catch it?

WATCH:

Quite a blow, huh?

Which is, of course, the message from the advertiser, Sandy Hook Promise, a nonpartisan nonprofit led by family members whose loved ones were killed at Sandy Hook Elementary School four years ago this month.

“Through “Evan,” we sought to show how different your perspective can be when you’re aware of the signs,” says Greg Hahn, chief creative officer of BBDO New York. “We’ve been fortunate to work with the inspiring people at Sandy Hook Promise to help parents, students and teachers better identify these signs.”

“When you don’t know what to look for, or can’t recognize what you are seeing, it can be easy to miss warning signs or dismiss them as unimportant. That can lead to tragic consequences,” says Nicole Hockley, co-founder and managing director of Sandy Hook Promise, who lost her first-grade son Dylan in the Sandy Hook massacre.

“It is important for us to show youth and adults that they are not helpless in protecting their community from gun violence—these acts are preventable when you know the signs. Everyone has the power to intervene and get help. These actions can save lives.”

Sandy Hook Promise says 80 percent of school shooters and 70 percent of individuals who completed suicides told someone of their plans before taking action—but all too often, no one intervenes.