A conviction for second degree manslaughter could actually be difficult in this case, considering the particular phrasing of Minnesota's second degree manslaughter statute:
609.205 MANSLAUGHTER IN THE SECOND DEGREE.
A person who causes the death of another by any of the following means is guilty of manslaughter in the second degree and may be sentenced to imprisonment for not more than ten years or to payment of a fine of not more than $20,000:
(1) by the person's culpable negligence whereby the person creates an unreasonable risk, and consciously takes chances of causing death or great bodily harm to another;
I've been browsing Minnesotan jurisprudence for a clarification, and I'll cite from State v. Frost, since it touches on the crux of the legal issue at stake here (warning: long wall of legalese incoming). I've bolded the most relevant parts:
State v. Frost
"The state contends that in interpreting section 609.205(1) this same definition of "culpable negligence" applies and that there is no requirement of awareness of risk on the defendant's part. In disagreeing with this, defendant points to language in our recent decision in State v. Zupetz, 322 N.W.2d 730 (Minn.1982), a case in which we held that second-degree manslaughter is not a specific-intent crime, and that therefore one may not be convicted of attempting to commit second-degree manslaughter.
"Recklessness" and "negligence" may be defined in the following manner: A person acts "recklessly" when he consciously disregards a substantial and unjustifiable risk that the element of an offense exists or will result from his conduct; the risk must be of such a nature and degree that its disregard involves a gross deviation from the standard of conduct that a law-abiding person would observe in the actor's situation. A person acts "negligently" when he should be aware of a substantial and unjustifiable risk that the element of an offense exists or will result from his conduct; the risk must be of such a nature and degree that his failure to perceive it involves a gross deviation from the standard of care that a reasonable person would observe in the actor's situation. The difference between the terms "recklessly" and "negligently," as thus defined, is one of kind rather than of degree. Each actor creates a risk of harm.
The reckless actor is aware of the risk and disregards it; the negligent actor is not aware of the risk but should have been aware of it.
Minn. Stat. § 609.205 (1980) defines second-degree manslaughter in terms of culpable negligence whereby the actor consciously takes the chance of causing another's death or serious injury; this definition corresponds with "recklessness" as defined by Wharton, supra. In Beilke, we called this kind of recklessness "intentional conduct which the actor may not intend to be harmful but which an ordinary and reasonably prudent man would recognize as involving a strong probability of injury to others...
...As Zupetz indicates, second-degree manslaughter under section 609.205(1) involves an element of awareness of the risk by the defendant. Stated differently, the statute requires proof of an objective element and a subjective element, the objective element being gross negligence and the subjective element being recklessness in the form of an actual conscious disregard of the risk created by the conduct.
This interpretation is based on the wording of the statute itself and, further, is in accord with the view espoused by the drafters of the Model Penal Code that liability for manslaughter should not be premised on "inadvertence to risk" (that is, disregarding of a risk of which one should be aware) but on a conscious disregarding of a substantial and unjustifiable risk of which one actually is aware."
The key takeaway here is that a conviction for second degree manslaughter requires the defendant to have taken a conscious risk. However, judging from the video the police officer genuinely believed she was firing her taser, so the element of conscious risktaking isn't being met. As State v. Frost shows, it's not enough to say that even though she wasn't aware it was her gun, she should have been (negligence), but the state must prove she was aware, but did it anyway (recklessness). From the currently available information, I don't see how the prosecution can prove the required element of conscious risk taking to score a conviction. The only opening for the prosecution would be if she consciously decided to wear her taser and firearm on the same side (which I strongly suspect would be against police department safety protocols), in which the case for manslaughter would become much stronger.
Good education at the beginning is great, but there also has to be continuing annual education and that does cost money.