Families of victims of the Sandy Hook shooting have come together to create a chilling video highlighting how easy it is to miss early signs of gun violence.

The disturbing film tells the story of a blossoming high school romance which ends with a tragic twist.

It features a character called Evan, a high school student bored at the end of term, who starts exchanging notes written on a table with an unknown classmate in the school library.

As their romance develops, the viewers’ attention is centred on whether Evan will ever find out who his mystery crush is.

When the two are finally introduced in the school’s sports hall, the chilling twist is then revealed as a student enters the room and loads a gun.

“While you were watching Evan, another student was showing signs of planning a shooting,” the screen reads.

Playing the video again, it highlights the shooter in the background behaving in an alarming way as well as being bullied.

The video is the work of Sandy Hook Promise, a Connecticut-based non-profit organisation set up following the Sandy Hook Elementary School shooting in 2012 by family members who lost loved ones.

Sandy Hook elementary school shooting 2012 Show all 5 1 /5 Sandy Hook elementary school shooting 2012 Sandy Hook elementary school shooting 2012 con0.ap.jpg Scenes of shock and devastation at the Sandy Hook Elementary School in Newtown, Connecticut AP Sandy Hook elementary school shooting 2012 v2Connecticut.jpg Picture from local newspaper the Newtown Bee shows Connecticut State Police lead children from the Sandy Hook Elementary School AP Sandy Hook elementary school shooting 2012 con1.reut.jpg The scene outside the primary school following the incident REUTERS Sandy Hook elementary school shooting 2012 con2.reut.jpg Concerned parents picking up their children following the shooting REUTERS Sandy Hook elementary school shooting 2012 obama.reut.jpg Obama wipes away a tear during the press conference REUTERS

Released on Friday, it’s part of the group’s wider campaign, “Know the Signs.”

The organisation's aim is to “prevent the senseless, tragic loss of life” caused by gun violence. Know the Signs encourages people to look out for signs of gun violence by highlighting that they could be happening right in front of you.