No, it wasn’t the only possible outcome but still a quite probable one.
Somehow I don't think they made this decision after siting down with a slide rule and a bunch of actuarial tables, so I don't know how they arrived at that balance of probabilities.
In reality it's more like cops defending their use of deadly force in any circumstances. They reckoned it had to be done, and their judgement is all that's needed to justify it, and now everyone else has to object to or rationalize their decision.