Six years have passed sinceNicole Hockleylost her son in theschool shooting at Sandy Hook Elementary Schoolin Connecticut, but his untimely death still brings tears when she least expects it.

Her son, Dylan Hockley, 6, died on Dec. 14, 2012, when a gunman stormedthe Newtown schooland fatally shot 20 children and six staff members before turning the gun on himself.

“In December, as I get closer to the (anniversary) date, I go on a large emotional rollercoaster,” Hockley tells PEOPLE. “I was driving to the train station yesterday and burst into tears for no reason — well, I know for what reason.”

ForMark Barden, who lost his son, Daniel, 7, in the massacre, the days leading up to the anniversary “are still just another day in the constant struggle,” he tells PEOPLE.

What helps both parents persevere is their work withSandy Hook Promise, the national nonprofit they helped found in 2013 focused on gun violence prevention.

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Starting Monday, SHP is unveiling itsnewest public service announcementto teach people how to spot the crucial warning signs of potential school shooters and to speak out before another tragedy steals more lives.

“Gun violence is preventable,” says Hockley.

Set in a high school in the days leading up to a school election, the fictional video,Point of View,shows warning signs of a shooter planning an attack.

The scene outside Sandy Hook Elementary School on Dec. 14, 2012.Shannon Hicks/Newtown Bee/ZUM

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“The warning signs are there almost every time somebody hurts themselves or someone else and our whole mission is to train people how to recognize them and report at-risk behavior,” says Barden.

SHP’s Six Warning Signs of Potential Shooters:

Proven Results

The information in the PSA — one of several SHP has rolled out since their firstaward-winning PSA,Evan, in 2016, which drew 155 million views on social media — andthe framework SHP createdto spot the warning signs are making a difference, says Barden.

“It works,” he says. “We have case histories and anecdotal evidence where mass shootings have been stopped and averted from the work we’re doing and from people following the model and uncovering something before it happens.”

Speaking up is easier, too, says Barden, “especially now that we have theSay Something Anonymous Reporting System, which has really taken off.”

This is critical, says Hockley, since the number of school shootings is greater than ever.

“There have been almost 100 school shootings this year alone so far and over 300 mass shootings so far,” says Hockley.

“What makes it more heartbreaking is not just that the violence is increasing but that these acts are so preventable,” she says. “People that they have actions that they can take and be part of the solution.”

Showing Compassion

SHP also teaches people to spot the signs of social isolation in someone who could be headed down a path of self-harm or harming others.

“These individuals are often loners, often bullied and often victims of isolation, so I hope that [the PSA] elicits feelings of compassion to report at-risk behavior and help get somebody connected to whatever services that they need,” says Barden.

“We can change this,” he says.

source: people.com