 Together with his friend and fellow Chief, "Mistāwasis" ("Big Child"), he signed the 1876 Treaty 6 as the second signatory chief at Fort Carlton, Saskatchewan.By signing this treaty he agreed to relocate his band to a 67 square miles reserve at Sandy Lake, 45 miles northwest of present-day Prince Albert, Saskatchewan.Ahtahkakoop was born about 1816 in the Saskatchewan River country.