The norwegians were quite lucky. Non annonced visitors aren´t welcome in drug controlled areas.

It is almost impossible to visualy diferentiate a "safe" poor neighborhood from a violent one in the outskirts of Rio.

In this case (and in other big cities in general) a good procedure would be to stay only in the main roads or in known tourist destinations. Don´t trust your map and GPS if it indicates a route througth smaller and smaller streets.

It is important to note that the violence in Rio de Janeiro is very localised. I was born in Rio and have never saw a shootout...

Fabio