In 2379 Shinzon, a Reman-raised clone of Jean-Luc Picard, killed the Romulan Senate and made himself Praetor of the Romulan Star Empire.
Shinzon was created by the Romulans as a clone of Picard, intended to replace him as a spy. When the plan was abandoned he was sent to work in the dilithium mines of Remus as a child. He rose to lead the Remans, and in 2379, backed by part of the Romulan military, he used a thalaron radiation device to kill the entire Romulan Senate, including Praetor Hiren.
Shinzon declared himself Praetor and invited the Federation to talks. The Enterprise-E was sent to Romulus. Shinzon had planted the android B-4 for the crew to find so that he could steal Federation information.
Picard soon discovered that Shinzon was dying from a failing genetic design, and that he needed Picard's blood to survive. Shinzon's true aim was to use his warship, the Scimitar, to wipe out the population of Earth with thalaron radiation. The plan was stopped at the Bassen Rift.