http://news.yahoo.com/s/nm/20080529/sc_nm/brazil_tribe_dc;_ylt=AugUG.MDU_1SMJj63Zp3eC6s0NUE"Rare uncontacted tribe photographed in Amazon "
The chopper is not making a single pass, it has circled/made at least a second pass. They were looking for this group, or if in the course of a routine flight they saw the village, they could have simply marked it and kept going and not buzzed them with the chopper. The men are clearly reacting to the intrusion defensively - bows are aimed up and at the chopper.