"We are sending this message in hopes of reaching the planet Earth. We have received your message. We are in dire times. The universe has begun its great collapse. It has swallowed many of our neighboring galaxies. Several of which had our colonies located inside. We hope that, should you receive this message, you heed our warning. We are long gone by now. We hope you are able to discover some way of halting this collosian crunch. Farewell, humanity. Farewell, universe. And good luck. The universe is counting on you."
Of course, this would be terrifying both in the sense that we weren't alone, are now, and we cannot stop a celestial event that will wipe out humanity.