On the morning of 17 or 18 June, the men were attacked by a band of Potawatomi, led by Mike Girty, probably those responsible for the Indian Creek massacre in May.

However, Sauk Chief Black Hawk and others disputed the treaty, claiming that the full tribal councils had not been consulted, nor did those representing the tribes have authorization to cede lands.

[3] Angered by the loss of his birthplace, between 1830–31 Black Hawk led a number of incursions across the Mississippi River, but was persuaded to return west each time without bloodshed.

[3] Finding no allies, he attempted to return to Iowa, but the undisciplined Illinois militia's actions led to the Battle of Stillman's Run.

[2] Prior to the attack, both Ament and Phillips were warned by Potawatomi chief Shabbona of impending danger to the settlers along Bureau Creek.

[2][5] The men arrived at Ament's cabin, 1.5 miles (2.4 km) north of present-day Dover, ate dinner and spent the rainy night at the site.

While the settlers ate dinner, a group from the sugar camp quietly concealed themselves in the underbrush and approached Ament's cabin undetected.

[2] The group has been named responsible for the May 21 Indian Creek massacre and the murder of a minister, Adam Payne, on the road to Ottawa.

[2][5] When the settlers awoke, Brigham and Phillips went onto the porch of Ament's cabin where they conversed for a few minutes, failing to notice the moccasin tracks around the property.

[5] Brigham, intending to accompany Phillips, entered his cabin for a moment, and once inside he heard the sound of musket fire outside.

[2] Dimmick's report of the incident was not well received by the people of Hennepin; it caused a general panic as citizens were convinced that Black Hawk's entire British Band was poised to attack the town.

[5][6] The Rangers formed a small detachment and set off in pursuit of the attackers but they soon gave up and returned to Hennepin with Phillips' remains.