Despite General Howard and Agent Monteith's outwardly projected confidence that the Nez Perces were about to yield to agency life, there is evidence that the settlers observing the gathering at Tolo Lake thought otherwise. Normally the assembly would have been viewed as a routine affair, for the tribesmen camped there annually. Several accounts suggest that, because of the recent debate at the Fort Lapwai council, the settlers expected a major outbreak, rumored to be scheduled to occur on July 4 at Mount Idaho as they celebrated Independence Day (despite it being more than two weeks beyond the date imposed for the Nez Perces going onto the reservation). Others indicate that a well-to-do Nez Perce cattleman named Black Tail Eagle warned the whites of imminent trouble as he passed through the settlements. On June 13, a Mount Idaho town father named John M. Crooks ventured out to the Nez Perce camp to find out what was happening. By now clearly anticipating trouble from the army, the tribesmen told Crooks that they did not intend to harm the settlers if they did not assist the soldiers.
Ultimately, the attacks came, but possibly in a more incidental manner than the settlers expected. The three warriors who initiated it on June 13, having failed to find Lawrence Ott, traveled to the ranch of Richard Devine, nine miles above Slate Creek, where they shot him to death and took his rifle. Reversing direction and heading north to John Day Creek, the three next day encountered Jurden Henry Elfers, Henry Burn Beckrodge, and Robert Bland, killing them and riding off on their horses. Continuing down the Salmon, they happened on storekeeper Samuel Benedict, out checking his cattle near the mouth of White Bird Creek, and wounded him. Benedict escaped. It was then that the warrior, Swan Necklace, returned to the gathering on Camas Prairie to boast of their exploits and recruit the other young men. Thus reinforced, the warriors attacked John J. Manuel's ranch, two miles above the mouth of White Bird Creek, wounding Manuel and setting his buildings ablaze. Encountering Samuel Benedict again, they shot him as he attempted to flee across White Bird Creek, killing him along with settlers August Bacon and James Baker. On June 15, the warriors continued their raiding, killing or capturing Mrs. Jennet Manuel and her eleven-month-old baby, and killing William Osborne and Harry Mason. Mrs. Manuel's seven-year-old daughter escaped with wounds. They raped two women, Helen Walsh and Elizabeth Osborn.  On the next day, a miner on the Salmon named Frank Chodoze was killed and his cabin burned. The crisis escalated with the killing by volunteers from Mount Idaho of a Nez Perce warrior named Jyeloo southwest of that community, and the Indians' retaliatory slaying later that day of settler Charles Horton. As the reality of the outbreak spread, fear mounted among the residents of Mount Idaho and Grangeville. 
In one of the most startling incidents of the outbreak, Benjamin B. Norton, proprietor of Norton's Ranch or the Cottonwood House, twenty miles northwest of Mount Idaho, sought to remove his family and guests to safety late in the evening of June 14. As the settlers' wagons proceeded toward Grangeville, warriors struck in the darkness, killing the horses, then shooting Norton, who died before morning, and wounding F. Joseph Moore, Lew Day, and Norton's wife, Jennie. Moore was an employee of Norton's, while Day had been en route from Mount Idaho to Fort Lapwai with news of the Salmon River killings. Both Moore and Day died later from their injuries. A nine-year-old son, Hill B. Norton, and eighteen-year-old Lynn Bowers, sister of Jennie Norton, fled into the night. In the suddenness of the assault, John Chamberlin and his infant daughter were killed and his other daughter wounded, while Chamberlin's wife was shot with an arrow and raped. Next morning, patrolling citizens found the survivors and ushered them into Mount Idaho before proceeding to the scene of the attack, about five miles west of Grangeville, and rescuing the wounded. The relief party narrowly escaped being attacked by Nez Perces advancing from Tolo Lake. 
Beyond the killings, the Nez Perces' raiding left widespread destruction, with many homes, barns, and outbuildings burned and plundered and horses, cattle, and hogs driven off or killed. There were frequent incidents of crops being destroyed. After their rampage along the Salmon, the warriors focused on farms and ranches on Camas Prairie, some near the lake where the bands had assembled. By then, most of the Salmon River settlers had found refuge at Slate Creek, where a stockade was raised, while others sought relief in Mount Idaho and Grangeville. At Mount Idaho, the small hotel was pressed into service as a hospital, and on a hill north of town, residents hurriedly threw up a circular barricade of logs, rocks, and sacks of flour. At Grangeville, an upright stockade was raised around the grange hall. Almost all the people who experienced losses filed claims within months, and most received smaller than requested awards over the next few years. 
There is no accounting for what happened in these attacks. Perhaps the events of June 1877 represented the culmination of a cultural crisis that had long simmered among the Nee-Me-Poo. The causes were many: Decades of cultural identity gone awry through repeated land swindlesby both the United States government and individual settlers. Missionary-inspired confusion over what the people should believe of the supernatural and the natural worlds, and over who the people were versus who they should be. The usual litany of broken promises. The repeated cases of physical abuse including the rape of Nez Perce women. The introduction of alcohol. The cupidity of crooked whites. The multitude of other Indian-white contact experiences that promoted grievances without redress. And all these issues led to the intratribal factionalism that had affected so many other tribes in similar ways.
The striking out by Shore Crossing and his followers against individual white men who had at various times wronged the Nez Perces only symbolized the deeper frustration wrought by the myriad issues and the outrage felt by all as they prepared to surrender the vestiges of their homeland. But what followed the first day's killings was a general outburst of the cultural angst that had fomented for years in the nontreaties' psychology, producing a displaced anger and aggression that could not be stemmed. It erupted after the initial Salmon River attacks, helped push the interband leadership away from the conciliation of the past and toward unreserved opposition to what was happening to their people, and reappeared in random explosions over the next three months as the tribesmen tried to elude the army. 
The events of June 14 and 15 happened with such swiftness that only on the latter date was the army at Fort Lapwai alerted, although Howard had received intimations of the discontent at Tolo Lake and had heard that the tribesmen might be reassessing their decision. On the fifteenth, Captain Perry sent out a detachment to determine why the Indians had not reported to the agency. The small mounted party had gone but twelve miles when they encountered messengers from Mount Idaho with the first report of the outbreak, whereupon they turned back to the fort with the settlers' plea for help.
Learning of the killings on the Salmon, and of statements by White Bird and Joseph that the people were not coming onto the reservation, General Howard promptly convened a meeting with Monteith, Inspector E. C. Watkins of the Bureau of Indian Affairs, and Captain Perry at Fort Lapwai. Howard directed Perry to ready his two companies to advance to Mount Idaho to relieve the citizens there. Simultaneously, Monteith sent out some friendly Nez Perces, ostensibly to bring in White Bird and Joseph, but more realistically to seek confirmation of the deaths. He then directed the agent at Kamiah to move his family and employees down to the Lapwai Agency. Later that day, news came from Mount Idaho that more whites had been killed. "We want arms and ammunition and help at once. Don't delay a moment," said the message. In answer, Perry's troops, outfitted with three days' rations in their saddlebags and enough for five more carried by pack mules, moved out at eight that evening accompanied by Nez Perce scouts from the agency. Through an aide dispatched to the telegraph at Walla Walla, Howard ordered up the two cavalry companies stationed at Wallowa Valley and the infantry at Fort Walla Walla. Howard then sent a dispatch to Major Wood at Portland requesting the concentration of more troops and supplies at Lewiston. He notified General McDowell of the situation, requested authority to hire more scouts, and closed reassuringly with, "Think we shall make short work of it." 
When Captain Perry rode out of Fort Lapwai, his fighting strength consisted of Companies F and H, First Cavalry, 103 men strong. In composition, the two companies more or less typified the enlisted ranks in 1877, many of them foreigners of diverse vocational background, including some recent recruits who were inexperienced in military matters, particularly in such basic cavalry requisites as riding and shooting.  Well outfitted for the work ahead, each man wore the issue black campaign hat (or perhaps a civilian-style hat), regulation blue army fatigue uniform, leather gauntlets and boots, and a loaded cartridge belt. Prescribed equipment included a tin canteen, haversack, shelter tent, saddlebags, and a leather carbine sling, and his weapons, consisting of the Model 1873 Springfield .45-caliber single-shot carbine and a holstered Model 1873 Colt .45 revolver.
The officers with the command were all veterans with western service. Connecticut-born Perry, age thirty-six, had been with the First Cavalry since the Civil War and possessed considerable experience of the Northwest Indian frontier. He had most recently participated in California's Modoc War of 1873, where he was wounded, and he owned two brevets for distinguished Indian wars service. Perry personally commanded Company F. His subordinate officer was First Lieutenant Edward R. Theller, attached from the Twenty-first Infantry at Fort Lapwai. Theller was from Vermont and had served with the California volunteers during the Civil War and with Perry during the Modoc campaign. Company H was commanded by Captain Joel G. Trimble, who, like Perry, had seen service with the First Cavalry since the Civil War. Trimble had fought at Gettysburg, Cold Harbor, and Five Forks, and he had been twice wounded in action. His second-in-command was forty-one-year-old First Lieutenant William R. Parnell, an Irish immigrant and veteran of European wars, including the famous charge of the six hundred at Balaclava. He had served with the New York cavalry during the Civil War before joining the regulars and gaining extensive experience under George Crook in Oregon and Idaho during the late 1860s. 
The troops traveled all night along the muddy Lewiston-Mount Idaho road, moving part of the way with skirmishers and flankers advanced to counter a surprise attack by the warriors.They reached Cottonwood and Norton's Ranch at about 10:00 a.m. on the sixteenth. After breakfasting there, they proceeded across the rolling Camas Prairie toward Mount Idaho, ascertaining from the smoldering haystacks and ranch buildings they spotted en route that they were entering the zone of conflict. Approaching Grangeville at sundown, they passed by Norton's abandoned wagon and dead horses. At Grangeville, frightened armed citizens presented Perry with details of the outbreak, informing him that a large body of Nez Perces had passed by on the prairie that morning headed in the direction of White Bird Creek on the Salmon. The troops bivouacked in a field, intending to go on to the vicinity of the attacks next day. That plan was scuttled after a delegation of townspeople convinced Perry of the necessity of moving forward and punishing the tribesmen before they crossed the Salmon. At 9:00 p.m., a trumpeter sounded "Boots and Saddles," and the cavalrymen made preparations for a night march. Eleven citizens volunteered to accompany the troops as guides, and all got underway by 10:00 p.m. 
For three hours, the soldiers groped south-southwest along the road toward White Bird Canyon, passing en route near Tolo Lake to assure that the Nez Perces had left that area. At about 1:00 a.m., they crested the rise leading into the canyon, the troopers halting to rest and await daylight. About 4:00 a.m., as dawn peeked over the eastern horizon, Perry ordered the march resumed and the cavalrymen started down through a steep and narrow gorge, traversing an old wagon road that led directly into White Bird Canyon. It was Sunday, June 17, and the soldiers moved forward with Company F leading the way in a column of twos, followed by Company H in identical order. Garbed in greatcoats, their carbines and revolvers at the ready, the command traced its way for several miles along a dry creek bed, occasionally skirting around undergrowth and generally paralleling the gradually widening canyon in its descent. Soon the soldiers encountered a woman and two children taking refuge in a ravine. The woman was Mrs. Isabella Benedict, whose husband had been killed by the warriors. Her four-year-old daughter had a broken arm. She told the soldiers that many tribesmen had passed down the canyon during the night.
The men gave the Benedicts food from their haversacks and a blanket, then moved down the grade, soon bearing into a broad valley several hundred yards wide, almost surrealistic in its grandeur and described as "rolling prairie . . . dotted here and there with wave-like swells."  The rising hillocks formed a perpendicular ridge dominating the distant front, while a long, rolling ridge paralleled the soldiers' left, beyond which White Bird Creek angled in toward the Salmon, several thousand feet below. One hundred yards in front rode Lieutenant Theller and an advance guard of eight men from Company F, while the citizens and several Nez Perce scouts from Lapwai Agency, riding on either side, served as flankers. In the increasing daylight, Theller's men, now moving up a gentle incline to the ridge in front, could discern an immense pony herd and, beyond that, distant warriors moving toward them. One of the volunteers recalled seeing loose stock running all about. "It was in the breeding season and stallions were fighting, mares squealing, etc., and the noise of all this made many of our horses hard to manage, so that many of the men were badly excited before the fighting began."