911 is an open API with no authentication. It cannot possibly prove guilt. Therefore, in a society which values innocence absent proof of guilt, police are bound to treat anyone they encounter by dint of information from 911 as innocent.
Also, it is not unlawful to carry a firearm in the USA nor in Kansas. Therefore, even if this person had been wielding a firearm, they are still to be regarded as innocent.
I'm actually of the mind that it makes sense to intentionally subject 911 to incorrect information (like we do with the TSA) in order to audit and pentest it.
We need a society where incorrect information given to open, authless APIs never leads to anyone's death.
And in fact, in this case, the officer who fired a weapon is, to my way of thinking, the only person at fault for this murder.
The caller is certainly an asshole and is even culpable for homicidal intent, but I don't think that their conduct is tantamount to murder - more like involuntary manslaughter. After all, with the exact same intent and the exact same conduct, they can reasonably expect that the other party is killed only a very small percentage of the time, and in every such case there is another more directly culpable party.
I'm also concerned, despite solid reasoning from many other commenters here, that any deference to the police officer in the form of pointing to mistaken information is a roadblock to advocacy of police reform.
In short: when the state murders someone, it's the state's fault. It doesn't make for a peaceful and just society to hold the state to the same low standard we hold some idiot CoD player.