Elsewhere, most of the Mato Grosso military district, including the commander, rose up in revolt. They stared at legalist forces across the Paraná river for a few days and gave up without a fight.
In the capital, all that was left on the 5th of July was the Copacabana Fort, which had been reinforced by other rebels, reaching over 300 men, had stockpiled supplies and formed a defensive perimeter with patrols, electrified wire and IEDs. A much larger legalist detachment surrounded them to the north and west, but did not enter into direct contact. The fort shelled military targets across the city. There are mountains between it and the city center, but for months in advance the plotters had calculated their ballistics. They did manage to hit the Army HQ, but as they were irresponsibly firing into a population center, they also smashed several residences and killed civilians. They also exchanged fire with other fortresses.

The legalists cut off their lights and water connections, and by the 6th of July the besieged Fort was in a hopeless position. Early in the morning, the rebels agreed to allow anyone to leave. Only 28 of them, including the commander, chose to stay. Two battleships and a destroyer sailed towards the Fort. The São Paulo hammered it with its 305 mm guns, and naval aviation dropped bombs. After noon, the commander left to negotiate - throughout all of this, they had negotiated by telephone - and was arrested. He left the Fort to lieutenant Siqueira Campos. There were three other remaining lieutenants. Siqueira wanted to shell the city and blow up the Fort with everyone inside, but the others disagreed.

Instead, they hammered their names with nails into the walls, split the national flag among themselves and went on a death march towards the presidential palace. Strolling through Atlântica Avenue along the beach, they interacted with civilians along the way. Most of the group ran away along the course, leaving a mythical number of 18, but it was likely 11. Long before they could reach the tunnel leading north out of Copacabana, a company of the 3rd Infantry Regiment was on the way. One of the four rebel lieutenants, Mário Carpenter, was himself part of the Regiment, a friend of the legalist platoon commander and subordinate to the company commander. They all had an angry discussion on the street. The legalists expected them to lay down their arms. Carpenter allegedly said:
Captain, we didn't come to hand ourselves in, we want to die in combat against you. It is, thus, useless to advise us.

Combat broke out, and the rebels took up positions on the beach, where there was a height difference. Unsurprisingly, they were defeated by the hail of bullets, but also took out a number of legalists. The company commander had orders to finish them with bayonets, but wanted to spare them. This task was left to the president's own police guard, who conducted the last bayonet charge. The rebels were taken to a hospital and even visited by the president, but most did not survive. Of the four lieutenants, only Siqueira Campos and Eduardo Gomes survived their wounds.