From the fall of 1967, he went on to study medicine at the Federal University of Rio de Janeiro (UFRJ). In Brazil, he became involved in the communist Araguaia guerrillas in the Amazon region. He went by the pseudonyms Paulo Paquetá and John Carlos Borgeth, and his fellow guerrillas didn't know his real name. He escaped the army in a suspicious manner in 1973 and had since disappeared from the guerrilla warfare. He was subsequently portrayed as a traitor by the army. In 1973 he left behind his fiancée Maria Célia Correa (Rosa), who had followed him in the guerrilla war in 1971. He knew Correa from the UFLJ where she had studied philosophy. She was arrested on January 2, 1974 and executed along with two others. It was not until 2003 that it was discovered that he had established himself as a doctor in Niteroi, where he provided acupuncture and shiatsu treatments.