Turning an Assault Case into a Homicide Case:
A bigger problem if you delay calling 911 or just walk away is that your action may lead to the aggressor’s death from the wounds you inflicted. If you wound an aggressor, walk away, and he dies from a wound you inflicted, and there is no intervening cause (negligence by an EMT or ER doctor, for example), then this may be a homicide case, not an assault case.
Homicide cases are much more serious, both in how they are investigated, whether the prosecution or police are willing to not charge you, and in the possible penalties if the jury decides your actions were not self defense.
A live assailant, who may have a long criminal record, is likely less sympathetic to jurors than a dead assailant’s parents, siblings, and children in the audience at your trial.
A live assailant showing his scars may be less sympathetic than autopsy photos and the cold, hard, deformed bullets pulled out of the body and entered as evidence.
Yes, a live assailant may lie about what happened, but your call for help for someone who tried to hurt or kill you speaks well of your character.
Homicide detectives and medical examiners may hear a less sympathetic story from a body left to bleed to death.