When Ford introduced the Model T and automobiles became popular, there was a rush to the Amazon in search of rubber. However, by 1913, rubber production had shifted to Malaysia, where trees could be planted and cheap labor was at hand. Those rubber tappers in the Amazon, called seringueiros, had to live in the Amazon and they performed brutal and perilous work to get small amounts of rubber for sale. Only the desperate were attracted to this work. These tappers did not expect to see anyone other than hostile Indigenous groups coming from the direction of the expedition.

On April 15, the group spotted a simple house, which was deserted. Next, the group encountered a man named Marques in a canoe. The man quickly paddled to shore. When the group, whose members were filthy and gaunt, explained that they were not hostile, Marques told them to signal that fact with three gunshots and a blow of a bamboo horn. When they encountered another house, they did so. However, the woman there was terrified, mistaking them for Indigenous forces, and fled downriver with her children. There, she told her husband, Honorato, that their home was under attack.