In reaction to the sacking of Lawrence by pro-slavery forces on May 21, and the telegraphed news of the severe attack on Massachusetts Senator Charles Sumner, John Brown and a band of abolitionist settlers—some of them members of the Pottawatomie Rifles—responded violently.

"[1]: 371 John Brown was particularly affected by the sacking of Lawrence, in which the Douglas County Sheriff Samuel Jones on May 21 led a posse that destroyed the presses and type of the Kansas Free State and the Herald of Freedom, Kansas's two abolitionist newspapers, the fortified Free State Hotel, and the house of Charles Robinson.

A Douglas County grand jury had ordered the attack because the hotel "had been used as a fortress" and an "arsenal" the previous winter, and the "seditious" newspapers were indicted because "they had urged the people to resist the enactments passed" by the territorial governor.

[2] The violence against abolitionists was accompanied by celebrations in the pro-slavery press, with writers such as Dr. John H Stringfellow of the Squatter Sovereign proclaiming that pro-slavery forces "are determined to repel this Northern invasion and make Kansas a Slave State; though our rivers should be covered with the blood of their victims and the carcasses of the Abolitionists should be so numerous in the territory as to breed disease and sickness, we will not be deterred from our purpose.

[3]: 163–166  In addition, two days before this massacre, Brown learned about the caning of abolitionist Charles Sumner by the pro-slavery Preston Brooks on the floor of Congress.

Letter of Mahala Doyle to John Brown, when he was in jail awaiting execution, November 20, 1859: "Altho vengence is not mine, I confess, that I do feel gratified to hear that you ware stopt in your fiendish career at Harper's Ferry, with the loss of your two sons, you can now appreciate my distress, in Kansas, when you then and there entered my house at midnight and arrested my husband and two boys and took them out of the yard and in cold blood shot them dead in my hearing, you cant say you done it to free our slaves, we had none and never expected to own one, but has only made me a poor disconsolate widow with helpless children while I feel for your folly.

NB [postscript] my son John Doyle whose life I begged of (you) is now grown up and is very desirous to be at Charleston [Charles Town] on the day of your execution would certainly be there if his means would permit it, that he might adjust the rope around your neck if Gov.

Late in the evening, they called at the house of James P. Doyle and ordered him and his two adult sons, William and Drury, to go with them as prisoners.

John Brown Sr. did not participate in the stabbing instead firing the coup de grâce into the head of the fallen James Doyle.

Glanville and Harris were taken outside for interrogation and asked whether they had threatened Free State settlers, aided Border Ruffians from Missouri, or participated in the sack of Lawrence.

Brown killed five in a single night, and the massacre was the match to the powder keg that precipitated the bloodiest period in "Bleeding Kansas" history, three months of retaliatory raids and battles in which 29 people died.

"The news of the horrid affair spread rapidly over the Territory, carrying with it a thrill of horror, such as the people, used as they had become to deeds of murder, had not felt before.

A United States congressional committee investigating the troubles in Kansas Territory identified Brown as the chief perpetrator.