Dog the Bounty Hunter‘s stepson Gregory Zecca has been placed on a psychiatric hold as he grieves the death of his son, who was killed in an accidental shooting at the Zecca residence.

A rep for the family tells TMZ … Greg has been put on a 5150 psychiatric hold because he is so devastated by the loss of his only son, Anthony … and we’re told there were concerns Gregory might try and take his own life.

The rep tells us the hold is because Greg is stricken by grief and not because he feels guilty of a crime in relation to the shooting.

We’re told Greg has not been able to speak to family or cops yet because he is heavily sedated.

TMZ broke the story … Greg shot and killed his 13-year-old son on Saturday in what we were told was a freak accident.

Cops say Anthony was shot in the neck and a gun was found on the island in the kitchen of their Naples, Fla., apartment.

Police are investigating and no one has been arrested.