The 64 coup was a lot like the Chilean one wasn't it? Where the congress of the country felt the left had so thoroughly infiltrated and co opted the Justice system and the political infrastructure that there was no way for Democracy but to do a hard reboot?
No, it was different from the Chilean coup.
There's a lot of story behind it which I'll omit here - the story of the 64 coup begins in 1945, when Vargas' fascistic dictatorship was brought down. Vargas started emphasizing the Labour aspects of its regime in early 1945, when he saw that he was going to allow free elections. The Labour faction of his government founded the Brazilian Labour Party(PTB), which, after the outlawing of the Communist Party, became the main leftist party in Brazil.
João Goulart, president of the PTB, was elected vice-president of Brazil in 1960(until then people elected separately the President and the Vice-President), and when the incumbent President resigned after 5-6 months of government, became president of Brazil. Meanwhile, the PTB was the fastest-growing party in Brazil, and had managed to become the second-largest party in Congress, after PSD(also founded by former members of Vargas' regime, but from the bureaucracy).
With that, PTB, which had mostly been a junior party in the PSD-PTB coalition that won most elections in the 1946-1960 period, started throwing its weight around, pushing for leftist policies, something which led to a reaction from the traditionalist sectors of the middle and upper class. This meant that the political scenario was chaotic(even the military high command was politically split), and Goulart, being the PTB leader, leaned on it and the PTB-associated labour unions for political support.
On March 13th, 1964, in a major Union rally, Goulart announces, among other measures, land reform on those lands owned by the Federal government. You can guess how people reacted to that. Even worse, on March 25th, a group of Navy enlisted personnel goes on 'strike'(by definition, a mutiny) - and João Goulart goes to the mutineers to hear their demands and show his support - this removes all pro-Goulart support in the military command. Even then, the military high command doesn't move at all, until General Olympio Mourão Filho, a(IIRC) division commander, goes 'fuck this shit, I'm going to take action' and orders, in the night of March 31st, his troops to move to Rio de Janeiro, where most of the government functions and Embassies still resided(Brasília had been founded 4 years before, but it would take almost 20 years for all administrative functions to move there).
As for leftist guerillas, we had them; Dilma Rousseff, former President(and eternal idiot), robbed banks as a member of a leftist guerilla movement. Still, neither their action nor their repression came close to reaching the number of deaths in Argentina and Chile(some 500-700 dead due to political violence).