Major spoilers for steelheart and possibly firefight ahead. You have been warned.
So, the other day I got thinking about who really killed steelheart. Yes, steelheart activated the trap, but David set it. David is the one who directly took action to cause steelheart's death. Certainly from a legal standpoint, that would be classified as David murdering steelheart, not a suicide. Does steelheart's powers not trace back intent like that? If so, what would have happened if steelheart had stepped into the path of a bullet? Would that count as coming from whoever shot the bullet, and is probably terrified, and thus be prevented or caused by steelheart and thus hurt him?
Another similar situation is at the beginning of the book with David's dad. He certainly didn't mean to hurt steelheart, but succeeded nonetheless. From what I can tell, steelheart's weakness seems to follow the following rule:
If whoever most recently took action that would hurt steelheart, regardless of knowledge or intent, is scared of him then that harm is prevented.
By this rule, the aforementioned situation with stepping into a bullet would hurt him.
Thanks for reading my ramblings! Let me know your thoughts.