A single mom nags her teen son into getting up and out the door to school. As an Aussie, she’s got one ultimatum that works every time.

“No school, no ‘footie.'”

They arrive, and she stays on campus with him. She’s a cop, and this is where she’s assigned.

But today is the day that justifies why police are assigned to schools where gun rights overrule human rights, as far as kids are concerned. “Active shooter!”

Today is the day everyone finds out how Policewoman Samantha Romans (Nadine Garner) reacts in such a situation. She calls for backup, draws her firearm and freezes. She weeps and cowers as kids flee all around her.

Her own son is among the 20 killed. Is his death the beginning of her torment, or the culmination of it?

Actor-turned-director Scott Major and screenwriter Christopher Gist take a flier on coming to grips with how people respond to the shock and terror of life-threatening danger, and bury that in a far-fetched thriller, “Line of Fire,” which was titled “Darklands” when it was released Down Under.

They flip the script, making Samantha the victim in a scenario that is common in American gunlands, where gun manufacturers, gun lobbyists and gun fetishists bend cowardly politicians into accepting that “cops in the schools” is the solution to an unregulated, often-deranged civilian subculture awash in machine guns.

How do you make a policewoman the victim? Not just by explaining “how these things happen.” As Samantha’s superior throws her under the bus (“She let everyone down.”), harassing phone calls and shouted insults from drive-bys begin.

And then that villain of the right wing gun culture sticks her nose in. Jamie is a laid-off print journalist hellbent on returning to relevance by getting Samantha to talk. Jamie (Samantha Tolj) smacks her lips over the payday that will lead to, the web traffic she can gin up for her website. She will not take “No” for an answer.

Her persistence turns into the ugliest harassment imaginable — shaming, blunt assessments of how Sam is being perceived, lies about how “I understand guilt,” published online taunts and then texting her quarry the crime scene photo of what a semi-automatic weapon did to her teen son’s face.

We barely have time to be appalled at this over-the-top terrorizing when out filmmakers flip the script again. Sam quickly concocts an absurdly detailed plan for revenge that will make her tormentor experience what she went through.

There’s merit in exploring just what leads to that “Lord Jim” moment when any person — soldier, sailor, police officer or civilian — finds out what we’re really made of. The psychology of panic, the knee-buckling terror of facing great peril to do the noble thing and try to save others makes for gripping drama, and in the case of mass shootings, fascinating “good guy with a gun” myth-busting.

But what Major and Gist have concocted trivializes the trauma with every “This reporter is the crazy one” and “She has that coming to her” turn.

Tense scenes of violence are undercut by the extremes that the shattered Sam indulges to in securing her vengeance. Her “particular skills” go far beyond that one expertise every cop on Earth carries into work each day, knowing the system and the people in it well enough to know just what one can get away with, and how.

“Line of Fire” can be unsettling and even wrenching when this or that aspect of the inciting tragedy is touched on and the viewer allowed the grace to consider what anyone — even someone trained to handle such scenarios — would face in such a situation.

But it stumbles from eye-rolling to infuriating all the way to risible as the filmmakers turn professional failure into armed and trained victimhood, and then into savage “learn your lesson” revenge.

Whatever merits this failed morality tale might have had are lost as it lurches into the ludicrous. The real shame here is worth pointing at the people who made this.

Rating: unrated, graphic violence

Cast: Nadine Garner, Samantha Tolj, Brett Cousins, Nicholas Coghlan and Texas Watterston.

Credits: Directed by Scott Major, scripted by Christopher Gist. A VMI Worldwide release.

Running time: 1:44