The leader of the Proud Boys, who was arrested in Washington shortly before the Capitol riot, previously worked undercover and cooperated with investigators after he was accused of fraud in 2012, court documents show.

Henry "Enrique" Tarrio helped law enforcement in a variety of investigations nearly a decade ago by providing information and going undercover, the records show.

The Proud Boys is a far-right, male chauvinist extremist group that seized on the Trump administration's policies and was a major agitator during earlier protests and the Capitol riot on Jan. 6. The Proud Boys have raile...