Camp Grant was situated at the confluence of the San Pedro River and Aravaipa Creek, the home of the Aravaipa Apaches before they had been driven from it by white settlers. In the Feburary of 1871 five starving old Aravaipa women came to the camp under a flag of truce, where Lieutenant Royal Emerson Whitman promised them santuary.
Before long over 500 Aravaipas, under Chief Eskiminzin had gathered there asking that they be allowed to grow crops along the Creek to feed their people. Whitman arranged for them to earn their keep by working as farmhands for the local ranchers and under his supervision ensured that they did not participate in any raids.
However at dawn on the 30th April a mob of angry citizens from Tuscon and their Papago mercenaries clubbed, shot, raped and mutilated 144 people, mostly women and children. Their actions were taken in 'retaliation' for a Gila Apache raid in which six people had been killed and some livestock stolen. The only surviving member of Eskiminzin family was one small daughter.
At the subsequent trial (demanded by President Grant, who threatened to put the state under martial law if the Governor failed to act) the jury took just 19 minutes to acquit all 100+ defendants. It did at least however show the Aravaipa were not responsible for the raid(s) that had been used to justify the massacre.