Maricopa County Sheriff's Office

Joe Arpaio.

Maricopa County Sheriff Joe Arpaio is mobilizing mounted posse to investigate the killing of at least one young wild horse in the Tonto National Forest. The volunteer posse could get to work as early as Tuesday.

They’ll be searching an area on the Salt River known as Pirates Island, where witnesses reported seeing a man Friday shooting at wild horses — and where a dead foal was discovered with wounds to its head and neck.

Sheriff Arpaio is calling upon his mounted posse for two reasons: “to try to scour the area, find any dead horses that have been shot,” he said, “and to send a message out, that we’re not going to put up with this. It’s almost like the Western cowboy days. The sheriff going after horse thieves.”

Witnesses described the shooter as a man wearing black shorts or underwear, and a dark green shirt. The sheriff’s department has a hotline for tips, and a local lawyer is offering a $1,000 reward for information leading to an arrest.