They took the wrong road and arrived in Morro dos Prazeres, Mr Cardoso said.
"They were accosted by traffickers. The victim was wearing a camera-mounted helmet, which the traffickers thought meant he was a police officer recording the incident, so they shot the victim, who died."
Mr Bardella was the third Italian killed in Brazil in three weeks, Italy's La Repubblica reported.
AFP reports that Mr Bardella and his cousin were travelling through South America on motorcycles and had arrived in Brazil after visiting Argentina and Paraguay.
Police have been attacked in the favela, which is near the scenic hilltop neighbourhood of Santa Teresa, several times in recent years.
The shooting comes amid an alarming rise in crime in Rio, despite efforts to reduce crime before the Brazil hosted the 2014 World Cup and Rio hosted the 2016 Olympics.
An economic crisis, rising unemployment and drained public security budgets have allowed drug traffickers and other criminal gangs to reclaim territory in many Rio neighbourhoods where police previously had the upper hand, according to Reuters.
In the lead-up to the Rio Olympics in August, the city's police staged a series of protests, including at Rio's international airport, warning visitors they were woefully under-resourced and ill-equipped to cope with the surging criminal activity.
This week Rio's new Mayor-elect suggested introducing a bizarre "mugging tax" for tourists so they city could afford to pay compensation to visitors who become the victim of muggings and armed robberies.
Tourists are warned to avoid favelas in Brazil's major cities, including Rio - even on organised tours.
"Crime levels in shanty towns or 'favelas' and many satellite cities are very high. Tourists should avoid these areas, even with a well-organised tour group, and especially at night," Australia's Department of Foreign Affairs and Trade says.
However, tourists say favelas that have been reclaimed by police are safer than others.
