Steven Douglas wanted to build a railroad to the pacific(east). The southern senators wanted to open territory in Missouri to expand and make land for slavery. 
John Brown got his sons or men to go arrest or kill people who owned or were owning slaves. Brown was a anti-slavery supporter and thought people had to be punished for doing this.
Charles Sumner criticized pro-slavery supporters and personally insulted Andrew Pickens Butler, a pro slavery senator. Preston Brooks beat Sumner with a walking cane until he was unconscious.