Background In 22 July 2011 a lone wolf terrorist managed to massacre 77 people, mainly youngsters participating in a political youth camp at Utøya Island outside Oslo. To meet the situation characterised as a national trauma a major psycho-social intervention was developed and implemented under the stewardship of health authorities and through consultations with experts, other central stake holders and the exposed themselves.

Methods The intervention was a large-scale pilot targeting the exposed (survivors with families, bereaved with parents and siblings) through a municipality-based individual and collective psycho-social follow-up model. The watchful waiting principle was replaced by pro-activity in the services. The individual needs in the victims were to be monitored by a health professional three times during the first year after terror. Individual contact persons providing a long time follow-up were pointed out in the municipal crisis units. National week-end and county-wise one-day reunions were arranged for the bereaved and the survivors with families. A large capacity building exercise was initiated in order to increase the competency of psychological trauma reactions and conditions in all relevant services.

Results Even if the effect of the interventions on the trauma related conditions is hard to measure there is convincing evidence for the benefit of the pro-active model as well as the benefit of the collective interventions, communicated by the service users themselves. The pro-active principle was embraced by all the exposed as were the national week-end gatherings for the bereaved. 99% of the latter evaluated the collective intervention as a good or very good help in their grieving process.

Conclusions Even if it is very difficult to evaluate the effect of the intervention model in terms of reduced symptom load in the exposed, pro-activity should be considered as one of the guiding principles in assessing the psycho-social needs of the exposed in major incidents in the future.