Umm.... that actually happened in 1867, nine years earlier

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On a side note, I think the term "massacre" is used much too inflationary whenever a battle (or in case of the LBH, part of a battle) ended with no survivors.
All those battles of the Indian wars, be it the "Grattan Massacre" of 1854, the "Fetterman Massacre" of 1866, or the "Custer Massacre", involved well-armed units who, usually through poor decision-making and other circumstances, found themselves in a situation without support and were wiped out when unit cohesion, vital for survival in the age of the single-shot weapon, collapsed.
But these were still battles, fights between armed men, not true massacres, like the Whitman massacre of 1847, where the Cayuse killed a group of missionaries, or the Sand Creek massacre of 1864, where the Colorado militia wiped out a Cheyenne village.