The Native American's used Buffalo for food, as well as for housing.
The Native American's ate almost all of the buffalo- except for the heart, as this was sacred and they buried this- and as soon as the buffalo population began to decrease, this meant that food became harder to find, which ultimately, will have lead to a number of deaths.
The Native American's also used the buffalo skin (or hide) to make the outside of their teepees, which will have kept them warm in the winter, as well as keeping them safe from the elements- therefore, as soon as the buffalo started to become rarer, this meant that they had to find other means to build new teepees.
Hope this helps :)
