I need some information about the lives and contributions of Gabriel Dumont and Louis Riel.

Gabriel Dumont (1837-1906) was a leader of the Metis (which has an accent on the "e"), one of the three indigenous people in Canada. The Metis combine indigenous and European ancestry. Dumont played a major role in the Northwest Rebellion (also called the Northwest Resistance), which was an uprising against the Canadian government in 1885 by indigenous people and their Metis allies in the areas now composing Saskatchewan and Alberta. His co-fighter in this rebellion was Louis Riel (1844-1885), also a Metis leader.
The Northwest Rebellion occurred as the Plains Indians were facing the destruction of their traditional way of life, as bison disappeared from the plains. Suffering from starvation, they also experienced having their land taken away in treaties with the whites, who fenced off the land in farms and towns. Railroads also disrupted the once unbroken plains. The Metis also depended on the bison and were experiencing the decline of their livelihood as fur traders. 
In 1884, Riel, who was living in the U.S. after leading the earlier Red River resistance, came back to Canada. The Metis composed a Bill of Rights, pressing their demands to the government, and they took over a church and formed a provisional government with Riel as head and Dumont as military leader. After a skirmish at Duck Lake with Northwest Mounted Police, the government sent reinforcements. Eventually, after a series of confrontations with federal forces, the Metis (not all of whom participated in the uprising) and their allies were defeated. Riel surrendered, and Dumont escaped to Montana. Riel was hanged in 1885 for his role in the five-month rebellion, and indigenous people were also hanged. The indigenous and Metis people suffered as a result of the uprising, as the indigenous people were taken over by the Canadian government. The Metis largely fled to Montana. Both groups lost a great deal of power in the aftermath of the uprising.