How did ordinary citizens become murderers? Were they responsible for their actions?

After watching all the lecture material and reading the assigned material, 3 pages. 

How did ordinary citizens become murderers? Were they responsible for their actions? What did you learn about these Ordinary Men including  Police Battalion 101 from the discussion in the video and the reading material? Since these perpetrators suffered no repercussions if they refused to participate in the killings, how do you evaluate their defense later on that they were just “following orders”? To what extent did the dehumanization of the Jews contribute to the ability of ordinary people to become killers?  You can use outside course (Not required). (You can answer each question separately).