EDINBURG -- An autopsy revealed what Hidalgo County Sheriff's deputies believe is the 18th murder investigated by the department this year.

Dr. Norma Jean Farley ruled that an unidentified man discovered north of Alton died from at least one gunshot to his head. Farley made the judgment from x-ray examinations during his autopsy.

Investigators could not obtain usable fingerprints from the man's body, which was badly decomposed when it was discovered Tuesday. No identification was found on the man's clothing, as well, according to a sheriff's office release.

Deputies say the man appeared to be between 25 and 35 years old, was about 5 feet 7 inches tall and weighed 200 pounds.

Investigators ask the public for help in identifying the body.

The man had a tattoo on his upper right arm -- a red, orange and black Yin-Yang symbol with flames spewing at one end. The flames are shooting towards his upper back

The man was also wearing a brown leather necklace with a beige, 2 inch long, plastic sea horse is attached to it.

Authorities received a call from a local rancher who found the body in his cow pasture about 3 p.m. Tuesday near the intersection of Los Ebanos Road and Mile 9, near Rancho Los Mirasoles.

Several abandoned homes lined the unpaved roads where the body was found.

Authorities urge anyone with information about the murder investigation to ocntact the Hidalgo County Sheriff's office at (956) 668-TIPS.