Yeterday's incident again put a harsh spotlight on security in the country, just six weeks before Brazil hosts the football World Cup, with Rio staging seven matches including the July 13 final.
The victim was in a stolen car and a firearm was found by his side, military police said after the shooting, which the G1 web portal reported came during a police crackdown on drug dealing and car thefts in the Morro de Chapadao slum.
It came nearly a week after police and people in a slum a short walk from the tourist haven of Copacabana beach clashed following the death of a dancer which residents blamed on police.
Separately, earlier yesterday, youths set alight three cars in the Alemao slum after the death of a 72-year-old woman in circumstances which remained unclear, G1 reported.
Since 2008 the Rio government has been rolling out a program of police "pacification," sending specialist units into 174 favelas in thrall to criminal gangs who have been fighting back to protect their turf.