By the time the detachment reached the Indian encampment, Auguste was intoxicated, and Grattan broke the translator’s bottle against his saddle. Had Lt. Grattan taken charge of Auguste at that point, and sent him back to the fort, it may have prevented tragedy. Instead, Lt. Grattan scolded him, and continued on. Auguste was not well liked by the Sioux, and spoke only broken Dakota, with his other dialects being poor to nonexistent. As they entered the encampment, he began to taunt the Sioux, calling their warriors women, and stating that the soldiers were not there to talk, but to kill them all. A local trader and trading post owner, James Bordeaux, later recounted those facts.
It is estimated that the encampment as a whole had some 1,200 warriors out of the total 4,000 or so total population. According to Bordeaux, Lt. Grattan did begin to realize his situation, and stopped to discuss this with Bordeaux, who was there trading. Bordeaux advised Grattan to speak directly with Conquering Bear and let him handle the situation in his own way and in his own time. Lt. Grattan seemed to grasp that concept, and continued on into the encampment. However, he first located the lodge of High Forehead, and ordered his surrender. High Forehead refused, saying he would die first.
Lt. Grattan then approached Conquering Bear, insisting that the Sioux should arrest the guilty party and turn him over. Conquering Bear refused. However, Conquering Bear did understand the nature of the situation and tried to negotiate, offered him a horse as compensation, but Lt. Grattan continued to escalate tensions. The problem was undoubtedly made worse by the interpreter Auguste, who continued to taunt the Sioux, and seemingly mistranslated some of what Conquering Bear said, as well as what Lt. Grattan said, as there seemed to be some confusion. Conquering Bear asked that the trader, James Bordeaux, be brought to translate, as they trusted him and his language skills were excellent. Bordeaux was notified by the Sioux, and he did ride forward to the meeting place, however he would later say that he could quickly see that the matter had gotten out of hand, as Lt. Grattan was openly defiant of Conquering Bear, and Bordeaux could see the Sioux warriors moving into flanking positions around the soldiers. Seeing this, Bordeaux departed and returned to his trading post, where he told his fellow traders to arm themselves, as a fight was coming.
Lt. Grattan evidently tired of the negotiations, and undoubtedly had noticed that his small detachment was in a bad position. He concluded the negotiations, and began walking back to his column. When Conquering Bear stood up, he was shot in the back and killed by a soldier, while another soldier fired into a group of Indians nearby, wounding one. This started a volley of fire from both sides; Grattan and the 30 men with him were quickly wiped out, with Lt. Grattan being one of the first killed. A group of some 18 soldiers did break away in an attempt to reach a small group of rocks so that they could form some sort of a defence, but were cut off and annihilated by warriors led by Red Cloud, then an up and coming war leader within the Sioux.
Conquering Bear was the only Lakota who was killed. Bordeaux was spared because he was married to a Sioux woman and had a friendly relationship with her tribe.