Background As a result of several violent terrorist incidents, authorities in Sweden have shifted from previous approaches of being certain that it is safe for the ambulance service to enter the scene, to a one where "safe enough" is sufficient, potentially making it possible to save more lives. The aim was therefore to describe specialist ambulance nurses' perceptions of the new approach to assignments involving incidents with ongoing lethal violence. Methods This interview study employed a descriptive qualitative design with a phenomenographic approach in accordance with Dahlgren and Fallsberg. Results Five categories containing conceptual descriptions were developed from the analysis: Collaboration, Unsafe environments, Resources, Unequipped and Risk taking and self-protection. Conclusions The findings highlight the need to ensure that the ambulance service is a learning organisation, where clinicians with experience of an ongoing lethal violence event can pass on and share their knowledge with colleagues to prepare mentally for such an event. Potentially compromised security in the ambulance service when dispatched to ongoing lethal violence incidents needs to be addressed.