After his defeat, Catiline started to champion the cause of Sullan veterans, the poor, dissolute aristocrats, and the dispossessed. When he was defeated again for the 62 consulship, Catiline started a conspiracy and had to leave Rome. Cicero obtained letters detailing the conspiracy, which he presented to the Senate. The Senate decided on an extra-legal action: to execute the leaders who were then in Rome. Then in January 62, a Roman force under M. Petreius defeated the Catilinarians near Pistoria and killed Catiline.
The main sources on Catiline are Sallust and Cicero.
E. Badian " Sergius Catilina, Lucius " The Oxford Classical Dictionary . Simon Hornblower and Anthony Spawforth. © Oxford University Press 1949, 1970, 1996, 2005.