GENESEO, N.Y. (AP) — A girl found shot to death in a western New York cornfield 35 years ago has been identified as a missing Florida teenager.

DNA from a half-sister confirmed the identity of 16-year-old Tammy Jo Alexander, who disappeared in the 1970s, the Livingston County sheriff's office announced during a news conference Monday.

Sheriff Thomas Dougherty said investigators had followed thousands of leads over the years, but the break in the case came in August when a former classmate reported to the Hernando County sheriff in Florida that Tammy Jo had been missing since between 1977 and 1979.

She had last lived in Brooksville, Florida, and attended Hernando High School.

Police contacted a half-sister and matched her DNA to the body found Nov. 10, 1979, in the rural town of Caledonia, about 18 miles southwest of Rochester. She had been shot in the head and back.

The victim's family had never reported her missing, according to a statement from the Hernando County Sheriff's Office.

"It's hard to imagine that someone could just throw a child away," former Livingston County Sheriff John York told reporters. "It's a great day to give her a name."

Police asked people with information about the shooting to contact the FBI.