A Brazilian woman aged 80 has helped police catch several suspected members of a gang that she filmed selling drugs outside her Rio de Janeiro apartment.
Brazilian police face a formidable opponent in Rio's slums
Police received two years' worth of secret videotapes made by the woman, leading them to arrest 15 people - including two police officers.
The tapes reportedly show children selling and using drugs in streets ruled by heavily-armed gangsters.
Clashes between drugs gangs are blamed for countless deaths in Rio de Janeiro.
The elderly lady, nicknamed the "granny-spy" by Brazilian newspaper Extra, now lives under police protection.
She used up 22 video cassettes, or 33 hours of tape, as she recorded the drugs gang's activities from her apartment window overlooking a hillside shantytown near Copacabana beach.
Pictures published in Extra newspaper appeared to show children - some seemingly less than 10 years old - using marijuana, cocaine and crack.
Many of the dealers appeared to be carrying pistols and sub-machine guns.
Rio state's Security Secretary, Marcelo Itagiba, praised the woman's efforts as a "victory for society" that proves "every citizen can contribute to the improvement of public security".
According to Extra newspaper, the surveillance tapes are accompanied by a running commentary from the "granny-spy".
"Just look at all these machine guns coming over here. Damn banditry," she was quoted as saying.
"Look at the future of Brazil. It is not possible that these children take this powder and no one does anything," she told the newspaper.
The newspaper said the crime-fighting pensioner was motivated by "indignation" and "desperation" at the police's alleged failure to combat the criminals.
The hunt is on for seven police officers implicated in the recordings, Mr Itagiba said.
Rio de Janeiro police have complained they are outgunned by the drugs gangs, who are blamed for a plague of killings and kidnappings in the city.