TULSA, Okla. — When a group began gathering signatures calling for a grand jury investigation into the beleaguered Tulsa County sheriff and his agency, the department spokesman declared that the sheriff would be open to a review and a chance to finally tell his side of the story “in a room that’s closed to the public with the district attorney and 12 citizens.”

Yet Sheriff Stanley Glanz now indicates that he will ask a judge Tuesday to throw out the successful petition signed by 6,647 citizens, another sign of mounting calls for his ouster since a volunteer deputy — a friend of Sheriff Glanz’s — fatally shot an unarmed man during an undercover operation in April. The sheriff alleges that the petition form was misleading and did not specify all of the allegations against him.

Civil rights leaders and relatives of the shooting victim, Eric Harris, questioned why the sheriff appeared to be backtracking.

“Glanz is afraid because he has no control; he has control over everything else but not the grand jury,” said Marq Lewis, an organizer with We the People Oklahoma, the group that collected the signatures. “The whole, entire office is afraid.”