Guilt can lead to shame, but what is the fact of shame? Social isolation, Withdrawal. The rejection of others, in shame based social orders. I think shame is the thing that makes your dog put its tail between its legs and hide. It is fear, but also a profound sense of withdrawal.
Clinically, I feel, the two manifested elements of trauma are dissociation and shame. The first detaches you from your instinctual emotions, which is to say from yourself; and the second detaches you from the rest of society.
The two combine to lead to the presenting symptoms of depression, anger, paranoia, intrusions, and the like. When you detach from the world, it becomes out there, and out there is not controllable or predictable. It becomes foreign ground, occupied by strangers. Everyone is a stranger, even the person looking at you in the mirror.
I think this is close to the truth. My work continues.
Edit: to be clear, I think most of tend to think people feel shame because of something. The most obvious example is incest, which transgresses rules we can be aware of consciously. But I don’t think this gets at the root of it, where there is no “because”. It is because it is. It is because it is built into us as animals. It is a direct nervous system level disruption of the social instinct.