Sanz was a good advisor to the Bolívar family and Simón lived in his house for two years, until he returned to his home again.
Together with José Domingo Díaz, he wrote between November 1810 and July 1811 the newspaper "Semanario de Caracas", the first unofficial publication of the First Venezuelan Republic.
After the Capitulation of San Mateo (1812), he was locked up in the dungeons of Puerto Cabello by the Royalist authorities, but he was released in June 1813.
When Bolívar occupied Caracas in August of the same year after the Admirable Campaign, Sanz joined the Republican cause again, participating in the establishment of the Second Venezuelan Republic.
At the request of General José Félix Ribas, who appointed him his war advisor, he returned to the continent but was killed on 5 December that year in the Battle of Urica, where the Republican troops were defeated.