The movie does describe the bombing and the 2011 Utoya massacre. The aftermath of victims is more graphic than the actual bombing and shootings.
The shooting on Utoya is also shown.
2 People get shot and then shot again in the head. No blood and from a distance.
Some teenagers get shot and you see them fall to the ground. No blood
Some teenagers and adults get shot in the camp building. You can see gunfire from a distance but no actual shooting.
Teenagers pretending dead get shot, but off-screen.