Fearful and moving, Utøya: July 22 is based on the massacre of 69 Norwegian Labour Youth League members by the 32-year old right-wing extremist Anders Behring Breivik , on the Norwegian island of the title, on July 22, 2011.

33 of the victims were under the age of 18. 99 young people were seriously injured in the shooting, and 300 of the holiday-makers were psychologically damaged by what they experienced. Breivik had set a bomb, which killed eight people, to explode earlier that day in Oslo’s government quarter.

These calamitous events have been recalled by director Paul Greengrass in another recent film, July 22, which, narrative-wise, has a wider scope. Poppe’s focus in Utøya: July 22 is solely on the island where there were 564 people around 5.30pm on that fateful day.

Most of them were having fun at their holiday camp tent settlement, chilling out, slagging each other, chatting each other up, eating, drinking, being flirtatious, when Breivik began to shoot. He fired 189 shots in total and it is entirely possible that director Poppe has let us hear all of those shots because his fusillade is the relentless sound-track to the film. We scarcely see the killer throughout the movie, just once in the distance in silhouette, as he takes aim on top of a cliff.

This Norwegian production relies on detailed testimonies from witnesses to fashion its amalgam of stories which have been worked by screenwriters Siv Rajendram Eliassen and Anna Bache-Wiig into a compelling and often brilliant narrative.

In other words, everything that happens to the lead character, the young resourceful Kaja (Andrea Berntzen) happened in real life to someone. Conversely, everything that happens to the other characters is based on an actual reality for someone who lived or died.

The movie features Norwegian actors who are clearly the same age as the deceased, they speak the same (Norwegian) language (with English subtitles in this case). They ask the same bewildered questions as they huddle together when the shots begin to ring out. 

The killer, it is noted, is dressed like a policeman, why would the police be shooting, they ask, is it an emergency drill of some kind. They call their mothers on mobile phones as the victims did, they call the emergency services, but that's another story.

The incidents recalled here are, in a way, much too close for comfort, given the huge native investment in the re-enactment. There is a sense that the actors are acting out of their skins by way of tribute to teenagers they or their families might have known. These young people were cut down in their prime in the woods, murdered at the shore, or as they tried to flee in the water.

Watching this disturbing, compelling film, one feels the cast have been driven by director Poppe to evoke the atmosphere of that day as though their lives depended on it. 

It is a film about young people literally running for their lives, huddling together under trees in dirt, trying to make decisions in hugely stressful circumstances, looking out for each other. Innocent youngsters hearing the boom of Behring Breivik's two guns yet again. Just when he seems to have ended his death-dealing crusade, he fires another round in an intermittent fusillade that lasts all of 72 minutes.

Accordingly, the film features a 72-minute apparently seamless take, drawn from footage shot over five days, a riveting sequence which takes us to a bleak finish with no apparent redemption. The film rather chooses to present in its closing credits a warning about the possibility of similar massacres happening again. 

Utøya: July 22 functions somehow as a documentary, in spite of its dramatic recreation of a recent event, and the scale and intensity of the collective trauma is evoked with astonishing, visceral power.

Open at Dublin's IFI on Friday.