Taking a fictionalized approach to a mass murder in Seattle a decade ago, Jagger Gravning’s “Wallflower” arrives at something more idiosyncratic and ultimately haunting than a standard docudrama-style true crime tale. Focusing less on the perpetrator than on the raver milieu he briefly infiltrated — to tragic results — this culture-clash snapshot provides a moving if also mysterious portrait of fragile mental health snapping tether entirely amid the alien environs of blithe hedonism.

Those looking for a more explanatory approach to Kyle Aaron Huff’s fatal shooting of six and himself in 2006 may be frustrated by the writer-director’s impressionistic view. But “Wallflower” is complex, empathetic and often poetical, emphasizing the flow of life that was interrupted rather than the interruption itself — in a way comparable to (though not as narratively abstract as) Gus Van Sant’s “Elephant.” It’s also a sort of nostalgia piece for the rave scene, whose candy-colored escapism as depicted here looks as archaic as hippiedom.

Huff isn’t named here (actor David Call is credited as playing “Murderer”), though the actions and minimally glimpsed backstory (in mostly eyeblink flashbacks) of his equivalent closely follow what’s known about him. But the characters he interacts with over the roughly 24-hour period depicted are fictive composites of the attack’s survivors and victims. A sense of profound internal stress is introduced in opening bits where Call’s bearded thirtyish loner, at once handsome and strangely anonymous, is heard apologizing for an act of drunken vandalism in his Montana home town, then leaving mercurial “crazy ex-boyfriend”-type phone messages for a woman we realize he may barely know at all.

Meanwhile, the inhabitants of a party house on E. Republican — notably a lesbian comic-book artist who’s dubbed herself Strobe Rainbow (Atsuko Okatsuka), and who is trying not to succumb to the bad vibes left by an ugly recent breakup, and her bestie Link (Conner Marx), the kind of compulsive prankster who can really be an irritant if you’re not in the mood for his antics — prepare for a big night. They’re inevitably going to a “Better Off Undead”-themed rave at the Capitol Hill Arts Center, as are many of their friends. A far less likely attendee is the Montana transplant, who appears to have a moralistic attraction/repulsion thing toward ravers.

As we see the shindig through his eyes, its playful psychedelia and outrageous self-expression become nightmarish, a dislocating mix of sexuality and grotesquerie he stands rigidly apart from. Yet simultaneously, he seems to plead for human connection. When a pretty younger woman (Hannah Horton as “Noobgirl”) asks if he’s OK, mistaking his barely restrained psychosis for a recreational-drug bummer, he places far too much significance on her kind gesture. Later Strobe likewise acts out of well-meaning pity when she invites this awkward-looking stranger to hang out at an after-party at her house.

There, too, everything that delights and diverts the inhabitants and their guests — the alternately childish and provocative behavior, the whimsical/disturbing art, the free flow of drugs and alcohol — seems designed in his mind’s eye to freak him out. His close-mouthed spectating strikes some as creepy voyeurism. When he speaks, he hits the wrong note, as when asking one free spirit if she’s old enough to be out all night with strangers. (The massacre victims included teenagers as young as 14.) The ravers pride themselves on inclusivity, but this dude feels like a narc, one whose judgmental air prompts a rare collective rebuff. That pushes his paranoias over the brink — and his body to the truck where he’s stowed a small arsenal of weapons.

The dawn shooting, while chronologically occurring at the end of this story (apart from a brief epilogue), is placed by Gravning near the start; his script then rewinds to chronicle the night of events that led up to it. This smart decision turns “Wallflower” from a thriller in which we simply wait for the bloody “payoff” into a drama about the people who had no idea what was waiting for them. (It’s unclear just how planned Huff’s actions were, though it turned out he’d left behind some ominous writings and a handmade fake bomb in the apartment building where he lived with his equally reclusive twin brother.) The result has a final impact something like Gaspar Noe’s “Irreversible,” in which there’s terrible poignancy to a fadeout in which we just begin to grasp the basic good nature and innocent hopes of protagonists whose awful fate we’ve already witnessed.

A long developmental process involving members of the raver community (Gravning himself had been invited to the “Undead” party) no doubt helped lend “Wallflower” its lived-in feel, which portrays that colorful milieu without the whiff of sensationalism it’s often acquired on-screen. Whether principals or recurrent semi-background characters like one called “Shroom Fairy,” the fictive fun seekers here can seem figures of vapid yet self-congratulatory immaturity to an outsider — yet to Gravning and co.’s credit, by the end we realize they’re using that immaturity as something to creatively explore and move through, hopefully to something greater.

As the oldest party person here with the most grown-up problems (relatively speaking), Okatsuka lends her character an assertive survivor’s strength, even as she indulges her appetites or temper. She emerges as a co-lead alongside Call, who powerfully etches a figure both frightened and frightening in his state of psychological extremis — one little-illuminated by dialogue or other intel here but fully inhabited in a performance that constantly sits on the edge of delusional meltdown.

There’s a textural richness to the film that amplifies the druggy raver experience and Huff’s paranoid perception of it, with outstanding work from Michael Solidum’s widescreen lensing, producer Robinson Devor’s editing and the design contributors. A busy, diverse soundtrack uses different versions of the Archies’ bubblegum classic “Sugar, Sugar” as an eerie, ironical running motif.

Film Review: ‘Wallflower’

Reviewed at Seattle Film Festival, June 8, 2017. Running time: 83 MIN.

  • Production: A Mending Pictures presentation in association with Paradigm Studio. (International sales: Paradigm, Seattle.) Producer: John W. Comerford. Executive producers: Robinson Devor, William Haugh, Mitch Greenblatt. Co-producers: Brian Nunes, Therese Lefebvre, Regan MacStravic, Dr. Richard S. Adler.
  • Crew: Directer, writer: Jagger Gravning. Camera (color, widescreen, HD): Mike Solidum. Editor: Robinson Devor. Music: Christopher Crooker.
  • With: David Call, Atsuko Okatsuka, Conner Marx, Cequoia Johnson, Hannah Horton, Hassan Cristos Messiah, Hope Shanthi, Joe Cummings, Jose Abaoag, Molly Tollefson, Nathan Haase, Rachelle Henry, Reza Leal-Smartt, Rosario Rieger, Stewie Valencia, Sheila Houlahan.