I need to make sure the telegram is anachronistically appropriate. In 1995, telegrams were still in use, though less common. So that's plausible. The killer might use a telegram for a nostalgic reason or as part of a meticulous plan to use various archaic methods.
I should draft a story where the detectives receive a telegram as part of the killer's communication. Let's say the killer is meticulous and uses different communication methods for each sin. For the seventh sin, he uses a telegram. The message is cryptic, and the detectives have to decode it to find the location of the next victim or to stop the final act. seven 1995 movie telegram link