I'm going with movie set. Noone is that fearless.
That's how common gunfire is there.
I wouldn't be surprised if it was that thing that just happened, were Brazilian cops did some kind of huge raid and it all went Wild West. We've seen stuff like that in Israel during intifada and a few other spats, Israeli troops sending hate down an alleyway and there are people standing there 30ft away just watching. It does take balls to stand in one spot when people are spraying automatic fire back and forth, but a paycheck could also be possible.