I already provided the answer in my first post:
8. If on view of the dead body and after personal inquiry into the cause and manner of death, the coroner considers a further inquiry and examination necessary in the public interest, the coroner shall make out the coroner's warrant directed to the sheriff of the city or county requiring the sheriff forthwith to summon six good and lawful citizens of the county to appear before the coroner, at the time and place expressed in the warrant, and to inquire how and by whom the deceased died.
More details are available at the link.
Yes, a Grand Jury is a non-judicial body which in those States that use them allows a Prosecutor to present before them reasons why he thinks a person has committed a crime, and then votes whether or not such evidence supports a criminal indictment charging a person with one or more crimes. It is not a trial, just (usually) a rubber stamp for the Prosecutor's office to get charges to court. This leads to a criminal trial.