Here is an excellent lecture by Sam Harris about how free will doesn’t actually exist. Here he talks about how everyone’s actions are a combination of genetics, previous events leading up to that moment, and randomness. He takes an in-depth look at every aspect of the concept of free will, including the moral, legal and psychological implications. He also refers to the fact that scientific studies have shown that our subconscious makes our decisions before our conscious mind is aware of what choice we want to make.
This gives more understanding to the concept of “we are all one”. Not only do the things that happen to us affect us, they ARE us. So everything anyone has ever done to us contributes to who we are, and everything we do to others affects who they are too.