My grandson shot himself in the head and his parents are wondering how to go about getting guardianship of him

You will need to file a petition for guardianship with the probate court in the county where your grandson lives.  Depending on the County, you typically have specific forms which need to be used.  The overall process is somewhat complicated.  You can check on the webpage for the Supreme Court of Ohio for some basic guidance.  The local probate court rules may be of assistance as well. Best of luck.