OP, really sorry this happened to you. Also sorry for all the weird responses blaming you for the problem.
This is one of the risks of too much automation: it can trigger mode confusion, which is a heightened risk when the driver is only half paying attention, if distracted by, for instance, a waiter arriving to hand you your dinner, and trying to complete that transaction.
If most of the time the hold feature works one way, and the auto park engage on door opening works one way, when confronted with a new scenario, likely the first time ever it did not work as expected, all the holes in the slices of swiss cheese aligned and a pretty bad accident happened.
I recently went through an exercise in UI development of turning off an electric scooter. We did not anticipate any scenario exactly like this, after brainstorming for hours over many weeks, with dozens of engineers, UX and product designers, civilian end users. Our situation by chance seems to cover this, but I will for sure add it to the list of possibilities (distracted user during power down, plus accidental throttle activation).
If I was responsible for any of this at Tesla, I would (internally) acknowledge the issue, and take ownership of mitigation of the risk, even if Tesla can be shown to not technically be directly at fault. They have a vested interested to not run over their customers.
If I were you, I would go back to the scene, once you feel better, and carefully see if you can re-create the failure.
Again, sorry this happened, hope you make a full and speedy recovery.