Circa 2076, a military unit commanded by Saavdra arrived on Tarakis, charged with evacuating the unwilling colonists. On the night the massacre occurred, the unit went to the colony's settlement, which was in a clearing surrounded by forest, and began rounding up the colonists for transport. The members of the unit were very tired and tense. The colonists were passively hostile to them. However, the unit noticed that 24 of them were missing. Just as the unit began to fan out to locate them, the 24 missing colonists began firing on them from among the trees. The unit responded by firing indiscriminately, killing the rounded-up colonists as they fled in panic. Some of the colonists sought refuge in a cavern, but they were killed by soldiers who inadvertently happened upon the cavern.
The unit left no survivors. To cover up the massacre, Saavdra ordered the bodies vaporized, which the soldiers did. He and the unit agreed among themselves to lie that they found the settlement deserted upon reaching it.
However, the colonists' fate did not long remain hidden. A monument to the massacre was built in a field on Tarakis. A synaptic transmitter was installed in it; this transmitter broadcast a neurogenic signal throughout the Tarakis system. This signal contained the memory engrams of the soldiers of the unit that committed the massacre, and had the effect of causing anyone exposed to it to vividly experience the massacre as if he or she had actually partaken in it. Since the signal permeated the entire system, the crews of ships passing through the system were exposed to the signal and experienced the effect. The power source for the transmitter was built to last for at least three hundred years, ensuring that the colonists' fate would continue to be made for many generations.
In 2376, approximately three hundred years after the massacre, the Federation starship USS Voyager, commanded by Captain Kathryn Janeway, passed through the Tarakis system and the crew was exposed to the signal. The crew experienced the signal's effect, resulting in intense psychological trauma to crewmembers, including Janeway and several senior officers. In investigating the seeming culpability of herself and her crew in the massacre, Captain Janeway led efforts which led to the finding of the Nakan memorial and its signal. Its power supply was discovered to be dwindling. Captain Janeway, against the strong recommendations of several of those of her senior officers who were affected by the signal, ordered the power supply replenished. This was to ensure the story of the massacre would continue to be made known. (VOY: "Memorial")