This story was originally published on Dec. 2. To mark the fourth anniversary of the Sandy Hook school shooting, it is being republished. 
 
 Sandy Hook Promise, an organization devoted to protecting children from gun violence that was launched in the wake of the Sandy Hook Elementary School massacre in Newtown, Connecticut, has issued a powerful public service announcement urging people to look for warning signs of potential shooters. 
 
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 In the Dec. 2 PSA, part of the organization’s “Know the Signs” campaign, viewers are introduced to Evan, a typical teenager, trying to find summer love as the school year winds down. We see Evan scratch “I am bored” into a desk in his school’s library, and he returns the next day to find a response from a female student. 
 
 Evan and the mystery girl scratch flirtatious messages back and forth, and Evan tries to find out who his secret pen pal is. On the final day of school, as yearbooks are being passed around for signatures, Evan’s chat partner recognizes his handwriting and reveals herself. But while she does, an ominous figure emerges through a door in the background, drops a large duffel bag, and cocks an assault rifle. 
 
 Viewers are then shown a shortened version of the same PSA: The message is that while viewers were distracted by Evan’s romance, they neglected the warning signs of a male student in the background who reads gun-enthusiast magazines, searches for gun videos on YouTube, and is bullied in the school’s halls. Towards the end of the PSA, viewers see the male student make a menacing gesture towards his teacher after receiving a poor test grade. 
 
 Text appears in the ad: “While you were watching Evan, another student was showing signs of planning a shooting. But no one noticed.” 
 
 The ad says, “Gun violence is preventable when you know the signs.” 
 
 “The PSA demonstrates how easy it is for one to overlook the signs of an at-risk individual demonstrating signs of violence, particularly gun violence, and that when one knows the signs, it can be prevented,” says a statement from Sandy Hook Promise. 
 
 The organization hopes the PSA will teach people how to recognize someone exhibiting at-risk behaviors and empower them to intervene. 
 
 Sandy Hook Promise states that 80 percent of school shooters and 70 percent of individuals who killed themselves told someone of their violent plans prior to taking action — yet nobody intervened. ||||| The onset of this PSA from Sandy Hook Promise, an organization created in the wake of the Sandy Hook Elementary School mass shooting in Newtown, Connecticut, begins innocently enough. The video follows a boy, Evan (the same name as the video), exchanging messages on a desk in the school library with an unknown classmate. 
 
 The flirtatious messages are sent back and forth until the end of the school year, leaving a dissuaded Evan without a chance to learn the identity of his secret crush. However, in a last-ditch effort to learn who the person is, he exchanges yearbook signatures with classmates — one of which recognizes his handwriting from the desk. 
 
 While the two begin talking, however, an ominous figure emerges from the entrance of the building, taking out an assault rifle and cocks the gun as the screen fades to black. 
 
 "While you were watching Evan, another student was showing signs of planning a shooting," the corresponding text reads. "But no one noticed." 
 
 The PSA then relays the scenes of Evan at school, and in the background are several alarming signs of another student looking at gun videos on YouTube, being bullied by classmates, sharing photos with a gun on Instagram and reading a gun enthusiast magazine. 
 
 Giphy The warning signs 
 
 "It's important to know that one warning sign on its own does not mean a person is planning an act of violence," the Sandy Hook Promise website reads under the "Know the Signs" program. "But when many connected or cumulative signs are observed over a period of time, it could mean that the person is heading down a pathway towards violence or self-harm. By knowing the signs, you have the power to intervene and get help for that person. Your actions can save lives." 
 
 The organization was founded by several family members whose children were killed in the Sandy Hook Elementary School mass shooting in 2012. The nonprofit's goal is to protect children from gun violence. 
 
 Watch the powerful PSA from Sandy Hook Promise below: ||||| It has been four years since a gunman walked into an elementary school in Newtown, Connecticut and opened fire, killing 20 first-graders and six educators before turning the gun on himself. 
 
 The Sandy Hook school massacre — its violence and wrenching loss, its heartbreak — still looms large for the survivors, whose lives were irreparably changed. 
 
 But their lives did not stop. In the years since the shooting, the survivors have continued on: raising children, giving back and thinking, sometimes, of the future. 
 
 On the yearly anniversary of the shooting, on Wednesday, PEOPLE spoke with three parents whose children were killed at Sandy Hook. We asked them about their lives now, about their families and about their hopes for the new year. 
 
 The Barden family in February 2013. Nigel Parry 
 
 Mark Barden 
 
 Mornings are still difficult for Jackie and Mark Barden, who lost their 7-year-old son, Daniel, in the 2012 shooting. 
 
 Each morning, after the couple’s two older children, James and Natalie, left for school each morning, Mark spent special one-on-one time with Daniel, snuggling on the couch or marveling at the snowflakes glistening on the tree branches outside the windows of their home before the first-grader boarded the bus. 
 
 Now, Mark tells PEOPLE, “Jackie and I still sit and have coffee after James and Natalie have left for school and just look at each other and say that we can’t believe our little Daniel is gone.” 
 
 In the weeks leading up to the shooting’s anniversary, “we have been recalling what we were doing on these same days in 2012, with no way to know what was looming around the corner,” he says. 
 
 “James and Natalie are probably doing better than Jackie and I are, but I think that has always been the case,” he says. “But that’s okay. That’s how it should be.” 
 
 Mark’s priority remains his wife and his kids, he says. James, now a high school junior, and Natalie, a high school freshman “are doing remarkably well.” 
 
 James, who plays soccer, “is thriving academically,” his dad says. “He is taking a bunch of AP [Advanced Placement] classes at school. He is cranking.” 
 
 Natalie, a school swimmer, “is doing well academically and has a nice, large social network.” She also seems to have inherited her father’s showbiz gene. 
 
 “Starting in February, she is going to host her own open mic night for kids,” says Mark, a musician who plays in his own band. “She has taken the initiative and is excited and busy with all of that.” 
 
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 Jackie “is managing,” Mark says. “Same as me. She gets a lot of strength from James and Natalie and our wonderful extended family that we are so fortunate to have, and from each other.” 
 
 The couple likes to keep “a close eye” on their children, Mark says. “We ride the balance between not dwelling on things [and] making the subject of Daniel’s untimely death something they feel comfortable speaking about,” he says. 
 
 But, Mark says, “It breaks my heart when little Natalie refers to Daniel in the present tense.” 
 
 Nicole Hockley testifies at the Illinois state capital in May 2013. Seth Perlman/AP 
 
 Nicole Hockley 
 
 For some, the future is difficult to consider. 
 
 “It’s a little hard to answer this, as I no longer do long-term planning in my personal life,” says Nicole Hockley, whose 6-year-old son, Dylan, died in the massacre. “I always used to have a plan, but I’m no longer that person.” 
 
 The few plans she has for the future, Hockley says, include focusing on her surviving son, Jake. 
 
 “I want him to be happy, balanced and continue to do well at school and in life,” she tells PEOPLE. “He’ll never truly know just how much I love him.” 
 
 She also wants to continue working with Sandy Hook Promise, a nonprofit organization she created with other Newtown parents in the wake of the shooting to protect children from gun violence. 
 
 Like Mark Barden, Hockley’s work with Sandy Hook Promise keeps her going. On Tuesday, they and other SHP members were in Washington, D.C., where President Obama signed into law the 21st Century Cures Act, which includes Connecticut Sen. Chris Murphy’s Mental Health Reform Act of 2016. 
 
 The bipartisan legislation aims, among other goals, to help serve American adults and children with mental health problems that go untreated or overlooked. 
 
 Members of SHP worked closely with Sen. Murphy and others to pass the act, Barden says. “I have heard that this is the most significant piece of mental health legislation to pass through our federal government in decades,” he says. 
 
 “We are very excited to be a part of all of this.” 
 
 WATCH : Father Returns to Sandy Hook Elementary For The First Time Since Son Jesse Lewis Was Killed 
 
 Hockley, Barden and other members of SHP are also proud of the “Know the Signs” prevention programs the organization started to help spot potential shooters, which included a powerful public service announcement on Dec. 2. 
 
 “We have trained more than one million students with our programs,” Mark says. “We have anecdotal evidence that the programs have stopped suicides, a school shooting and have brought bullying down to near zero in some districts.” 
 
 Besides raising her son, Hockley says her other priority is to continue working with SHP and “keep saving lives.” 
 
 “It’s the only way I can prevent more families from grieving like mine,” she says. “It’s the way my family wants to honor Dylan.” 
 
 Scarlett Lewis in February 2013. Nigel Parry 
 
 Scarlett Lewis 
 
 Scarlett Lewis, who lost her 6-year-old son, Jesse, in the shooting, is focusing on raising her oldest son, J.T. Lewis — who, like his mother, is trying to help others. 
 
 In September, J.T. was given the “Courage Award” at the Teen Choice Awards for his work with Newtown Helps Rwanda, an organization he founded, which provides college and post-graduate education for orphaned genocide survivors. 
 
 “He is doing amazing,” Lewis tells PEOPLE. “He just raised enough money to pay for one of the survivors to go to grad school. He paid for one year.” 
 
 Lewis, who wrote 2014’s Nurturing, Healing Love: A Mother’s Journey of Hope and Forgiveness, is also working to bring her Choose Love Enrichment Program to as many schools and communities as she can. 
 
 “Since Sandy Hook, there have been more than 200 school-related shootings,” Lewis says. “All of them could have been prevented with social and emotional learning. I think social and emotional learning could also have prevented the tragedy at Sandy Hook. 
 
 “It’s a different way of thinking, but it seems so obvious: Kids who are able to give and receive love won’t want to harm one another.” 
 
 Helping others doesn’t take away the pain and suffering of losing her son, Lewis says. But Jesse’s death has given her perspective. 
 
 “The greatest life lesson I received in all of this is that we are all just here to help one another,” she says. “I didn’t know that four years ago, but I feel incredibly blessed to know it now.”
– Meet Evan. He's a bored high school kid who starts defacing school property, er, doodling on a table in the library one day. Someone writes back. Messages are swapped as days pass, mystery and romance bloom. Evan wanders the halls, eyeing his classmates, wondering who his mystery penpal is, and as AdWeek puts it, "there ensues a back-and-forth that's pretty captivating. Perhaps too captivating." (To avoid spoilers, stop reading and watch the video.) The end result has been described as "jarring" (Kansas City Star), "chilling" (Mic), and "powerful" (People). While you and Evan are busy being captivated—especially as Evan meets his mystery penpal—one of Evan's classmates is lurking in the background providing warning signs that he's planning a shooting, which in fact interrupts that very meeting we've been waiting for. The ad comes courtesy of Sandy Hook Promise, run by family of the victims of the school shooting in Newtown, Conn. "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," says Nicole Hockley, whose 6-year-old son, Dylan, died in the massacre. The organization, which says 80% of shooters tell someone what they're planning, aims to shine a light on the need to watch for those signs. (In Utah, a teen's own parents disarmed him inside a school.)