was killed on this date in 1890. 
Sitting Bull was a Hunkpapa Lakota chief and holy man. He was born around 1831 on the Grand River in present-day South Dakota. He became a warrior in a battle with the Crow at age 14, subsequently becoming renowned for his courage in fights with the U.S. Army.
In 1874, an expedition led by George Armstrong Custer confirmed the discovery of gold in the Black Hills, an area that had been declared off-limits to white settlement by the Fort Laramie Treaty of 1868. When efforts by the government to purchase the Black Hills failed, the Fort Laramie Treaty was abrogated. All Lakota not settled on reservations by January 31, 1876, would be considered hostile. Sitting Bull led his people in holding their ground.
As the PBS web site New Perspectives on The West describes it
In March, as three columns of federal troops under General George Crook, General Alfred Terry and Colonel John Gibbon moved into the area, Sitting Bull summoned the Lakota, Cheyenne and Arapaho to his camp on Rosebud Creek in Montana Territory. There he led them in the sun dance ritual, offering prayers to Wakan Tanka, their Great Spirit, and slashing his arms one hundred times as a sign of sacrifice. During this ceremony, Sitting Bull had a vision in which he saw soldiers falling into the Lakota camp like grasshoppers falling from the sky.
Inspired by this vision, the Oglala Lakota war chief, Crazy Horse, set out for battle with a band of 500 warriors, and on June 17 he surprised Crook’s troops and forced them to retreat at the Battle of the Rosebud. To celebrate this victory, the Lakota moved their camp to the valley of the Little Bighorn River, where they were joined by 3,000 more Indians who had left the reservations to follow Sitting Bull. Here they were attacked on June 25 by the Seventh Cavalry under George Armstrong Custer, whose badly outnumbered troops first rushed the encampment, as if in fulfillment of Sitting Bull’s vision, and then made a stand on a nearby ridge, where they were destroyed.
Public outrage at this military catastrophe brought thousands more cavalrymen to the area, and over the next year they relentlessly pursued the Lakota, who had split up after the Custer fight, forcing chief after chief to surrender. But Sitting Bull remained defiant. In May 1877 he led his band across the border into Canada, beyond the reach of the U.S. Army, and when General Terry traveled north to offer him a pardon in exchange for settling on a reservation, Sitting Bull angrily sent him away.
Four years later, however, finding it impossible to feed his people in a world where the buffalo was almost extinct, Sitting Bull finally came south to surrender. On July 19, 1881, he had his young son hand his rifle to the commanding officer of Fort Buford in Montana….
Though well-known for his appearances with the Buffalo Bill Wild West show, Sitting Bull actually was only with the show for four months in 1885, during which he was paid $50 a week to ride once around the arena.
Returning to Standing Rock, Sitting Bull lived in a cabin on the Grand River, near where he had been born. He refused to give up his old ways as the reservation’s rules required, still living with two wives and rejecting Christianity, though he sent his children to a nearby Christian school in the belief that the next generation of Lakota would need to be able to read and write.
Soon after his return, Sitting Bull had another mystical vision, like the one that had foretold Custer’s defeat. This time he saw a meadowlark alight on a hillock beside him, and heard it say, “Your own people, Lakotas, will kill you.” Nearly five years later, this vision also proved true.
In the fall of 1890, a Miniconjou Lakota named Kicking Bear came to Sitting Bull with news of the Ghost Dance, a ceremony that promised to rid the land of white people and restore the Indians’ way of life. Lakota had already adopted the ceremony at the Pine Ridge and Rosebud Reservations, and Indian agents there had already called for troops to bring the growing movement under control. At Standing Rock, the authorities feared that Sitting Bull, still revered as a spiritual leader, would join the Ghost Dancers as well, and they sent 43 Lakota policemen to bring him in. Before dawn on December 15, 1890, the policemen burst into Sitting Bull’s cabin and dragged him outside, where his followers were gathering to protect him. In the gunfight that followed, one of the Lakota policemen put a bullet through Sitting Bull’s head.
Tatanka-Iyotanka describes a buffalo (bison) sitting on its haunches.