Construing a traumatic event as central to one's life story and identity is associated with posttraumatic stress. The longitudinal relationship between centrality of event and trajectories of posttraumatic stress was examined. Data from ministerial employees were collected 10 months, 2 years, and 3 years after the 2011 Oslo bombing (N = 259). Using structural equation modeling, the launch and the snare hypotheses were tested. Support for the launch hypothesis was found; higher levels of event centrality 10 months after the attack were associated with higher levels of posttraumatic stress across time. Support for the snare hypothesis was also found; higher levels of centrality 10 months and 2 years after the bombing were related to higher levels of posttraumatic stress, beyond what could be anticipated based on the individual's general trajectory. This suggests that event centrality can influence the overall trajectory, and may also have additional time‐specific effects on posttraumatic stress.Copyright © 2016 John Wiley & Sons, Ltd.