There is nothing absolute about it at all. As the investigation could lead to adverse actions not of a criminal nature, either administratively or via civil process (wrongful death suit).
Based on the "use of force" doctrine of DHS (which this officer falls under) there is no justification for deadly force unless there is an imminent threat of death or serious bodily injury upon the officer or others.
That is your opinion. While your opinion has value, it doesn’t hold the same weight as the opinion of the prosecutor or a grand jury.