Tracy Gilpin (Photo: Courtesy of the Massachusetts State Police)

For more than three decades, the killing of Tracy Gilpin remained unsolved.

But on Sunday, the authorities in Plymouth County, Mass., announced a breakthrough: They had made an arrest.

Two days earlier and 700 miles away, the police in Troutman, N.C., helped Massachusetts state troopers arrest Michael A. Hand, 61. Rendition proceedings are underway to bring Mr. Hand back to Massachusetts, where he will be charged with murder, according to the office of the Plymouth County district attorney, Timothy J. Cruz.

Ms. Gilpin, of Kingston, Mass., was 15 when she disappeared on Oct. 1, 1986. Three weeks later, her body was found in a park in neighboring Plymouth. Her skull was fractured, and her cause of death was determined to have been blunt head trauma, probably sustained the night she vanished.

Her older sister, Col. Kerry Gilpin, went on to become the superintendent of the Massachusetts State Police. On Sunday, Colonel Gilpin praised the many law enforcement agencies that worked to identify and arrest a suspect.

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