Why are you and others ignoring the fact that each time they had showed up before the man had never been a threat. And according to CNN, was "hundreds" of times. Now I doubt it was hundreds, but I'd be willing to bet it was enough to think "we've got to go here and make him take his meds again." Nothing more, nothing less.
Yet this time he showed up with a weapon and attacked the officers.
Complacency? Sure. Just not in the way you're implying. Had they gone in on high alert it might have ended differently. But I can tell you from personal experience you get called out to a particular residence enough, you know what happens and you get complacent. Is it right? No, because you should always expect the unexpected. But on the same token, they probably have done it enough times not to consider that person a threat. And if you consider the positioning of the officers, their tone, inflection, their stance and demeanor, you can see they aren't going in with hostility or anything else. There are no barked commands, no pistols drawn from the beginning. Just two random cops going to a residence that has been visited multiple times in the past and (likely) always ended with guy taking his meds and everyone going away happy.
And again, you have less than a second to decide to get stabbed or fight. Flee was not an option as I stated before.
Your choice.
The same people she had called before and completed the call without incident how may times?
Don't ignore the history here. It's very central to the argument.