“We have found conclusive evidence that police and military in Peru used disproportionate, indiscriminate and brutal force against protesters and bystanders,” César Muñoz, the Americas associate director at HRW, told Al Jazeera. “We can say that with certainty.”

The report, released on Wednesday, comes nearly five months after widespread demonstrations erupted across Peru, following the impeachment and arrest of then-President Pedro Castillo in December.

After reviewing autopsy and ballistic reports as well as health records, HRW found that most of the protester and bystander deaths were the result of gunshot wounds.

Of the 49 civilians killed during clashes with security forces from December through February, the nonprofit found that 39 died from firearms, and five more were killed by “pellets fired from shotguns”.

According to Muñoz, police, in some cases, used a type of lead pellet that contravened Peruvian law.

“The national police of Peru have approved pellets for use in crowd control operations,” Muñoz said. “But those pellets are supposed to be made of rubber.”

One civilian, 22-year-old Rosalino Florez, was shot more than 30 times with pellets on January 11. He died this past March after nearly two months in the hospital.

Another protester, Víctor Santisteban Yacsavilca, was killed on January 28 when a police officer used a riot gun to launch what appeared to be a tear gas canister at a group of protesters in the capital Lima.

HRW’s review of CCTV footage shows Santisteban collapsing, with blood streaming from a wound to his head.

“It really saddens me as a person, as a human being, as a sister… to see that we live in a country where there is no justice,” his sister Elizabeth Santisteban said.

“It really makes me very sad that 60 lives are worthless to this corrupt government,” she added, using an estimate for the overall death toll from the protests.

The protesters have issued a broad range of demands. Some have called for the release of Castillo, who faces charges of “rebellion” for attempting to dissolve Congress and rule by decree in the face of a third impeachment hearing on December 7.

Other demands include new elections, the dissolution of Congress and the resignation of President Dina Boluarte, the former vice president under Castillo and the first woman to assume the top role in Peru’s government.

A February survey from the Institute of Peruvian Studies showed Congress had a disapproval rating of 90 percent, while the president’s disapproval rating was at 77 percent.

While Boluarte has apologised and expressed “regret” for the deaths, she has stopped short of resigning.

“I will not resign. My commitment is with Peru,” she said in January. She has also blamed the violence on so-called “radicals” in the protest movement.

Wednesday’s report also details multiple instances of protester violence, including hurling rocks at police and setting fire to buildings. HRW also verified videos showing that some protesters used fireworks against officers in Juliaca, the city where 17 civilians and one police officer were killed in January.

However, the report notes that the protesters’ actions are no justification for the “brutal, indiscriminate, and disproportionate response by security forces”.

It also accuses the Peruvian government of “apparent inaction” in the face of alleged abuses against protesters.

Although Attorney General Patricia Benavides has opened probes into the protesters’ deaths and into President Boluarte’s response, HRW has found “serious flaws” in these criminal investigations.

These alleged flaws include instances of failing to conduct autopsies before burials and a failure to seize police officers’ weapons for “ballistic analysis without delay”.

The nonprofit called for further accountability in its report. “As of early February, the Ministry of the Interior had not opened any investigation into police conduct and no police officer had been disciplined or removed from duty,” HRW wrote.

But it also pointed to systemic hurdles that have impeded justice, as part of the “deteriorating rule of law” in Peru.

“Sectors of government have been taking action to weaken checks on their power,” the report explained, claiming that corruption was a “major” issue and that Congress had pursued “steps to undermine the independence of the national electoral system”.

For Ursula Indacochea, the program director at the Due Process of Law Foundation, justice will only come when Peru accepts international assistance in investigating the protest violence.

International assistance “has happened in very similar cases in other countries”, Indacochea told Al Jazeera. “If the government accepted this support, it would be an important political gesture demonstrating that it really is committed to justice.”