The documentary film Tower offers a jarring reminder of mass murders on college campuses and schoolyards. With its intense focus on the mid-day horror at the University of Texas, Aug. 1, 1966, Tower presents a painfully personal look at the 96 minutes of hell that unfolded long before the need for the active shooter emergency drills commonly practiced at schools today.

A few survivors have broken their silence and recounted that awful day, giving new background on this first mass school shooting.

Directed by Keith Maitland, Tower has its television premiere on Independent Lens at 10 p.m., ET, Feb. 14 on PBS (check local listings). No doubt, this is not a film that couples will want to curl up with on Valentine’s night, but it’s worth noting that Tower won the Grand Jury Prize at Austin’s 2016 SXSW Film Festival, and that should be enough incentive to at least schedule it for recording.

Maitland notably gets the story of the first shooting victim – Claire Wilson, then an 18-year-old freshman, was leaving an anthropology class with her boyfriend and crossing the South Mall when shots rang. Wilson was eight months pregnant and critically injured.

Maitland also blends archival footage of the scene at the 27-floor University of Texas Clock Tower along with rotoscopic animation. The interviews are stirring recollections, the animation is somewhat distracting – but give the director credit for quilting together the dramatic moment-by-moment recounting of events.

Young Tower viewers ought to note that police tactics were not yet in place to respond to mass shootings. Communication ranged anywhere from difficult to impossible which meant coordinating a response to the gunman isolated at the top of the observation deck was improvised and dangerous – there were no cellphones. Also, several civilians had grabbed their weapons and began shooting back, endangering police who were trying to reach the gunman, Charles Whitman.

Also, after police officers finally made their way to the observation deck, despite uncertainty about the shooter, and shot him to death, hundreds of people crowded onto the plaza, damaging what today would be “an active crime scene.”

The focus of Tower is on the victims, and not much said about the profoundly disturbed Marine veteran who killed 13 people and wounded more than 30 others. The Associated Press reported that he had killed his wife and mother prior to heading to the University that day. One victim died in the hospital a week later, and medical examiners eventually attributed 17 total deaths to Whitman as late as 2001 – including a man who had been shot and wounded in his one functioning kidney and chose to stop dialysis treatment.

And just in case the blurry film clips and the animation make Tower seem too detached and clinical, two broadcast clips illuminate harsh truth: an Austin TV anchor asks on camera that a section of the victims’ names be repeated and he hears that one is his namesake grandson, a student at U of T. Finally, a Walter Cronkite report on the shooting plays as the soundtrack for other TV news clips showing what has become a sad, sad roll call of school shootings.