After exchanging a few shots with some Confederates on the outskirts of town, Lane's Brigade entered the settlement with two pieces of large artillery and immediately began to ransack it, starting with the bank. After blowing open the safe, they were disappointed to find no money there, but only a few documents. Allegedly, the citizens of Osceola, having heard of the incoming soldiers, had hidden the money before their arrival. Sentries were posted at the town entry points to stop any help from approaching and anyone daring to do so, was fired on immediately.

Enraged, Lane ordered his men to pillage and burn the entire town. The courthouse was broken open and the county records destroyed, stores and private homes were pillaged and torched, and buildings were bombarded with cannon balls. It was not long before the city was a smoking mass of ruins.

 
If this was not enough of an atrocity, twelve men were given a farcical trial and shot on the town square. These men, who had tried to defend the town, were "convicted” of treason and condemned to death by firing squad, of which Lane himself took part. Amazingly, three of them would survive, but Lane was not aware of this or he probably would have returned to kill them. 

Finally, Lane's men brought their frenzy of pillaging and murder to a close by celebrated by getting drunk, so much so, that according to reports, many of the men were unable to march when it came time to leave many and had to ride in wagons and carriages. With them, they took their plunder including Lane's personal share, which included a piano and a quantity of silk dresses. The troops then continued to Kansas City, Missouri. The settlement suffered more than $1,000,000 worth of damage including that belonging to pro-Union citizens.

Lingering fury regarding the Osceola Massacre stirred hatred in many a Missouri citizen and would become one of the causes for William Quantrill’s raid on Lawrence, Kansas two years later on August 21, 1863.

Lane was severely criticized for his actions in Osceola, most severely by General Henry Halleck, Commander of the Department of Missouri, who believed that the attacks made by Lane and Colonel Charles Jennison, aggravated anti-Union sentiments in Missouri and intensified resistance to federal authority in the state. Of their actions, he would state: "The course pursued by those under Lane and Jennison has turned against us many thousands who were formerly Union men. A few more such raids will make this State unanimous against us." Thus, Lane's Brigade was ended.

Two years later, when William Quantrill attacked Lawrence, Kansas in what has become known as the Lawrence Massacre, Confederate guerillas could be heard shouting, "Remember Osceola!" Though Lane was in residence in Lawrence at the time, he was able to escape the attack by racing through a cornfield in his nightshirt.