Nearly four years after the Sandy Hook Elementary School shooting, parents and community members from Newtown, Connecticut, have released a powerful campaign to highlight warning signs exhibited by potential school shooters.

In the video, a romantic story plays out for the protagonist, Evan, red-haired teenager in search of a mystery girl at his high school.

Evan can't wait for summer break, and he sketches a message of boredom into a desk at the school library. Someone has written back and a dialogue starts between the boy and the mysterious pen pal.

The much-awaited encounter between Evan and the mystery girl is cut short when a single gunman appears behind them at the school's gym entrance.

"While you were watching Evan, another student was showing signs of planning a shooting. But no one noticed," states the video before rewinding and highlighting how another student appeared to be planning a shooting in the background of Evan's story.

The video closed with a black background and white text reading: "Gun violence is preventable when you know the signs".