Many people were flooding into Kansas these people were either Pro or Antislavery. They did this because those who were in Kansas were allowed to vote and determine if Kansas was a slavery state or not.
Kansas and Nebraska Act.
People sat down to vote to determine if Kansas was Pro-slavery or not. It was ultimately voted as a Pro-slavery state. This didn't go well with many and then created a free state legislature making another government which was anti-slavery
This obviously started problems and violent actions. Mobs from Missouri and other pro-slavery states came into Kansas killed people and burned houses, and printing presses.
John Brown and other anti slavery people came in from the northern states to pull 5 men out of there beds and murder them this was called the Pottawatomie Massacre.
John Brown" Raid on Harpers Ferry
John brown led a group of men into Harpers Ferry in the attempt to steal the guns and have slaves and other African Americans to help in a revolt. The Successfully took the armory.
No Slaves or Free African Americans showed up and John Brown ultimatley got arrested after multiple people died at the scene. John Brown and all the others that were captured were executed and led to the the nations different opinions on the subject.