[2] Garnier has been accused by generals Mauro Cid and Carlos Baptista Júnior of plotting a coup with former president Jair Bolsonaro to overthrow Brazilian democracy in 2022,[3][4][5][6] and he is being formally investigated for his involvement since 2024[update].

He concluded his studies at the Navy School in 1981, as the first in the Armada Corp. As Lieutenant, he served the União and Independência frigates and the Escola Brasil ship.

According to the Ministry, Garnier is Master in Operational Research and System Analysis at the Naval Postgraduate School, in the United States, MBA in International Management at the Federal University of Rio de Janeiro (UFRJ) and course of Politics and Maritime Strategy at the Naval War School for two years.

[3] As Admiral of the Fleet, he had served as Secretary-General of the Ministry of Defence during the administration of minister Fernando Azevedo e Silva, until 9 April 2021, when he assumed office as Commander of the Brazilian Navy.

On February 8, 2024, the Federal Police launched Operation Tempus Veritatis to investigate a criminal organization involved in the attempted coup d'état and the abolition of the Democratic Rule of Law, aiming to gain political advantage by keeping the then-president of the Republic in power.