The facts are stark. On July 22 in 2011 Anders Behring Breivik detonated a bomb in Oslo, killing eight people. Two hours later on the Island of Utøya dressed as a policeman he randomly gunned down and killed 69 young people who were on the island at a summer camp.

Kaja (Andrea Berntzen) talking to her mother faces the camera, breaks the fourth wall, then turns back. And with this turn director Erik Poppe pulls the viewer into Kaja’s world.

Poppe quickly establishes the sheer size of the camp, with the tents closely clustered together, the amount of people participating. Kaja has had words with her sister and fallen out, meanwhile the youths are setting about having a good time, with banter and flirting. They have heard about the incident in Oslo and are reassuring relatives. We hear noises in the background. We know they are shots but to the people in the camp they are background noises in a rural setting. That’s until people start running into the camp panicking, its then those noises start to become distinctive.

The camera stays with Kaja; the situation develops but confusion reigns. Slowly it starts to clarify that they aren’t safe and have to move. Kaja tries to call her sister as her little group look to escape into the forest from what they don’t know. They come across bloodstained colleagues with garbled words about the police but they have little or no idea what is going on.

The gunshots just ring out in the rural air, at times constant for them to fall away, then start again. There’s no respite as Kaja makes her way away from her companions back to the camp to look for her sister, in a state of almost complete incomprehension.

Utøya lasts 92 minutes - the duration of the attack - and does not let the viewer go for one second. We are in with Kaja and her companions as they experience the panic and terror, and confusion. As such there’s no real narrative just situations that Kaja has to deal with: a traumatised little boy who will not move and a shot girl, struggling, in a desperately moving scene. Berntzen’s film debut is an accomplished multi-layered performance of great skill and pathos.

The power of this film is that we know what is happening from the outset and Poppe’s method’s while involving also has us as helpless observers which is at times overwhelming. The film is based on survivors’ accounts, the characters are fictional. So there is the drama of how this will end and that could well be the main issue with this film.