The term “homicide” being used is a bit ambiguous. Illegal homicides are varying degrees of murder and manslaughter. So one wouldn’t see a charge of simply homicide, since there are homicides that are not chargeable offenses.
A Governor can ask, that's about it. A Prosecutor (or an Attorney General) has what is called Prosecutorial discretion.
Prosecutorial discretion. (except in the case of General Michael Flynn, then the Judge Sullivan in that case wants to be Judge, Prosecutor, and Hangman) is when a prosecutor has the power to decide whether or not to charge a person for a crime, and which criminal charges to file. This is a rather broad power that also gives prosecutors the authority to enter into plea bargains with a defendant, which can result in the defendant pleading guilty to a lesser charge or receiving a lesser sentence for pleading guilty to the original charge. An example of this is a police officer letting you go with a warning when they could have charged you with speeding.
The above is just a small / limited over view of Prosecutorial discretion.