Alexander's heir apparent, Constantine, had privately declined the succession, unknown to the court, and his younger brother Nicholas decided to seize power as Tsar Nicholas I, pending formal confirmation. While some of the army had sworn loyalty to Nicholas, a force of about 3,000 troops tried to mount a military coup in favour of Constantine. The rebels were weakened by dissension between their leaders, but confronted the loyalists outside the Senate in the presence of a large crowd. In the confusion, the Tsar’s envoy was assassinated, and the loyalists responded with heavy artillery which scattered the rebels. Many were sentenced to hanging, prison or exile to Siberia. The conspirators became known as the "Decembrists" ().