This article reports the follow-up results of our field study (Jarero & Uribe, 2011) that investigated the application of the eye movement desensitization and reprocessing (EMDR) Protocol for Recent Critical Incidents (EMDR-PRECI) in a human massacre situation. A single individual session was provided to 32 forensic personnel of the State Attorney General in the Mexican state of Durango who were working with 258 bodies recovered from clandestine graves. Pre-post results showed significant improvement for both immediate treatment and waitlist/delayed treatment groups on the Impact of Event Scale (IES) and Short PTSD Rating Interview (SPRINT). In this study, we report the follow-up assessment, which was conducted, at 3 and 5 months posttreatment. Follow-up scores showed that the original treatment results were maintained, with a further significant reduction of self-reported symptoms of posttraumatic stress and PTSD between posttreatment and follow-up. During the follow-up period, the employees continued to work with the recovered corpses and were continually exposed to horrific emotional stressors, with ongoing threats to their own safety. This suggests that EMDR-PRECI was an effective early intervention, reducing traumatic stress for a group of traumatized adults continuing to work under extreme stressors in a human massacre situation. It appears that the treatment may have helped to prevent the development of chronic PTSD and to increase psychological and emotional resilience.