Flashbulb memories are a concept presented by Roger Brown and James Kullik in 1977, which they described as particularly vivid memories “for the circumstances in which one first learned of a very surprising and consequential (or emotionally arousing) event”. In their paper, they proposed that in the case of such events, our memory of it remains vivid over a long period of time. The authors also suggested that there might be a brain mechanism which specifically facilitates flashbulb memories.
Source: Brown, R.; Kulik, J. (1977). “Flashbulb Memories”. Cognition. 5 (1): 73–99.