Updated

A Brazilian prosecutor has charged a Rio de Janeiro police officer with homicide in last April's killing of a 10-year-old boy during a police operation against suspected drug traffickers in one of the city's largest slums.

The charges filed by Homero das Neves against officer Rafael de Freitas Rodrigues challenge police findings that the officer fired in self-defense and that 10-year-old Eduardo de Jesus Ferreira was caught in crossfire.

The boy's mother, Terezinha Maria de Jesus, has said she saw a police officer shoot her son.

Forensics showed the shot that killed Ferreira came from a policeman's weapon

The charges filed by Neves said the police officer shot randomly without any proven aggression from drug dealers.

"The circumstances surrounding young Eduardo's death could become a watershed moment in the fight against impunity and this is an important step by the Public Prosecutor to ensure external oversight over police actions," Atila Roque, executive director of Amnesty International Brazil, said in a Thursday statement. "This is crucial when we are talking about a police force that has killed more than 1,000 people between 2014 and 2015 in alleged confrontations. Transparency in this investigation will be a way to protect everyone."

Amnesty International said that while the "internal investigations say the boy was killed by a stray police bullet during a gunfight with armed criminals, testimonies from the family, neighbors and even two of the police officers involved have raised doubts over whether the confrontation took place at the time of the killing."