Saavdra was the Nakan commander of the troops that massacred 82 settlers on Tarakis in the 21st century. He gave orders to evacuate the Nakan colonists. When the colonists resisted, the troops panicked and opened fire.
Saavdra tried to cover up the massacre by vaporizing the dead bodies. But a synaptic transmitter was erected so that the fate of the colonists would never be forgotten. This transmitter would cause those who came into contact with it to relive the massacre. (VOY: "Memorial")