Officials with Sandy Hook Promise say many such shootings followed warning signs that were either ignored or misunderstood.
The PSA was shot by some big-name Hollywood filmmakers, including "Snow White and the Huntsman" director Rupert Sanders.
The group says the short piece "bring(s) to life the mind of a school shooter as he plans an attack."
"We tried to show the perspective of school violence through the eyes of a potential shooter, seeing all the signs and signals along the way," group founder Nicole Hockley said. "The chronic isolation, the bullying, the obsession with firearms."
Its release coincides with the sixth anniversary of the December 14, 2012, shooting in Newtown, Connecticut, which took the lives of 20 children and six educators.
"The signs and signals of someone who is at risk of hurting themselves or someone else are there," Hockley said. "We know that four out of five school shooters tell someone else. Seventy percent of completed suicides give off warning signs and signals. We're just not trained on how to recognize them."
Hockley founded the group just six months after her son Dylan was killed in the shooting.
"When we first launched, we started on the policy front, legislating for background checks, doing a lot of advocacy work," she said. "And when that didn't pass in 2013, we realized we were approaching this problem from the wrong way."
The team that produced the PSA has also produced two others with Sandy Hook Promise. Combined, they have been viewed 3 billion times, part of the effort to continue the national dialogue about preventing gun violence -- which is exactly what Sandy Hook Promise set out to do.
(The Associated Press contributed to this report)
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