I don't think there really was one particular event but many that shaped me. I came from a pretty chaotic childhood filled with moving a lot, loss, mental illness, addiction, drugs/alcohol and violence. Exposed to just over all unhealthy behavior. Which I think has made me want to stay as far a way from that in my personal life now as an adult.
However, I do have a strong drive to help people in need. I know how it feels to to be in the mix of all those problems. I have great compassion and as long as it doesn't come into my home around my children I do try to help. I do agree with you that childhood events do shape who you are but as in my case does not give anyone the right to hide behind that and treat others badly.