Unfortunately, in times like these, prosecutors may decide to file inappropriate charges to curtail the anger and violent protesting, which they also might hope that if the person is acquitted one or two years later, then the anger will have subsided and not be as intense.  Though, it looks like Minnesota has varying degrees of "murder" (however, I just read a piece where even their 3rd Degree of Murder, which the officer has been charged with, may be difficult to convict on due to a need to show intent or not caring if the person dies or not).  See, this is why in Illinois "attempted murder" is so hard to prove because it has to be proven the offender intended to kill the victim. 

But the prosecutor has also charged several things (which some of the pundits and laypeople don't fully understand why it is not just a murder charge - in this incident, they seem to have the thought that it somehow lessens the level of this offense which they feel is murder and that manslaughter lessens the importance of the offense if manslaughter is also charged - they fail to see it as sort of throwing all kinds of offenses against the wall hoping one or more will stick in a trial).

As for if Trump's re-sending of the "only good Democrat is a dead Democrat" - well, here in Illinois that would not be an assault because in Illinois an assault charge carries a required element of "reasonable apprehension of a battery." For example, if I were on the shoreline and yelled to a person in a boat on the water how I was going to kick his/her ass, it wouldn't be an assault because the person was safely away. So some other offense would have to be used.  In Illinois, it would possibly be disorderly conduct.  

But there are offenses such as "communicating a terroristic threat" or the like.

I find it so sickenly hilarious how thin-skinned "tough" Republicans are when Democrats say shit like "deplorables"....and forgetful, too..