While there are a number of factors at fault here, including widespread corruption and increased drug activity, the police bear some responsibility in the recent killings in Brazil. Better training, better pay, and more police could help to reduce the killings. More accountability could also reduce the amount of killings.
There's been a spike in the number of people killed by police as Brazil approaches the Olympics. Maybe it's part of a security effort, but the increase is way more than 100% compared to the past year. Without knowing the details of each incident, it sounds like there's not a process of justice here, but I can't say for sure.
Yes, Brazilian police are at least partly at fault for the increase in killings. They should make sure that no innocent people are caught in the crossfire when a shooting occurs. Even though we can't completely blame the police for these rise in killings (it's definitely mostly the criminals' fault), police should be more aware of who they are shooting.
No, the Brazilian police are not at fault for the increase in killings. The increase in killings in Brazil are the result of a number of forces coming together at the same time that has led to a volatile situation within the country which needs to be resolved before the Olympics. It is not fair to place the blame on the police.