This is your response to me clarifying that homicide includes both involuntary as well as voluntary homicide?
The fact that you think a federal trial (on what grounds? deprivation of civil liberties) would follow a state trial (on a charge ranging from involuntary manslaughter to murder in the first degree) means you either don’t know what you’re talking of, or your think the state won’t obtain a conviction.
To my knowledge, the suspect has not yet been charged. This indicates that the police are still gathering information so as to determine to what crime the evidence points.
It means that this case is so big that not only will the state prosecute, but there are federal prosecutors waiting in the wings to file charges.