The incident occurred July 10 in the Buckeye Hills at Gillespie Dam.
Department officials said they have reason to believe a group of five men seen leaving the scene in two vehicles may have been involved.
"We rely heavily on the assistance of the public in coming forward with information, and we are hopeful that a tip could lead us to those responsible for this heinous criminal act," said Ryan Randall, wildlife manager. "This is a horrible waste of the state’s most precious resource, its wildlife."
The reward for information leading to an arrest in the case now stands at $5,000.
The Game and Fish Department’s Operation Game Thief program has offered $2,500 for information leading to a conviction. The Arizona Desert Bighorn Sheep Society has offered an additional $2,500.
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