Stan Patz, father of 6-year-old Etan Patz, speaks to reporters after Pedro Hernandez, the man convicted of killing 6-year-old Etan Patz, one of America's most notorious missing-child cases, was sentenced at Manhattan Supreme Court, in New York, Tuesday, April 18, 2017. (AP Photo/Mary Altaffer)
Stan Patz, father of 6-year-old Etan Patz, speaks to reporters after Pedro Hernandez, the man convicted of killing 6-year-old Etan Patz, one of America's most notorious missing-child cases, was sentenced at Manhattan Supreme Court, in New York, Tuesday, April 18, 2017. (AP Photo/Mary Altaffer) Credit: Mary Altaffer

NEW YORK — Almost four decades after first-grader Etan Patz set out for school and ended up at the heart of one of America’s most influential missing-child cases, a former store clerk convicted of killing him was sentenced to at least 25 years in prison.

In a few angry words, Etan’s father condemned the convicted man.

“Pedro Hernandez, after all these years, we finally know what dark secret you had locked in your heart,” Stan Patz said. “I will never forgive you. The god you pray to will never forgive you. You are the monster in your nightmares.”

His wife, Julie Patz, wiped tears from her eyes as she witnessed the culmination of a long quest to hold someone accountable for their son’s disappearance. The case affected police practices, parenting and the nation’s consciousness of missing children.

The lead defense lawyer, Harvey Fishbein, told the court Hernandez wanted to express deep sympathy to the Patzes but also to say “he’s an innocent man and he had nothing to do with the disappearance of Etan Patz.”

Hernandez was a teenager working at a convenience shop in Etan’s Manhattan neighborhood when the boy vanished in 1979, on the first day he was allowed to walk alone to his school bus stop.

Hernandez, who’s from Maple Shade, New Jersey, confessed to choking Etan. But his lawyers have said he’s mentally ill and his confession was false, and they vowed to appeal his conviction.

In a sign of the case’s impact on the law enforcement officials and everyday people enmeshed in it, the courtroom audience Tuesday included Manhattan District Attorney Cyrus R. Vance Jr., police officers who worked the case and a half-dozen ex-jurors.

Etan was among the first missing children pictured on milk cartons. His case contributed to an era of fear among American families, making anxious parents more protective of kids who many once allowed to roam and play unsupervised in their neighborhoods.

The Patzes’ advocacy helped to establish a national missing-children hotline and to make it easier for law enforcement agencies to share information about such cases. The May 25 anniversary of Etan’s disappearance became National Missing Children’s Day.

“Now,” he said after the sentencing, “I know what the face of evil looks like.”

From the start, Etan’s case spurred a huge manhunt and an enduring, far-flung investigation. But no trace of Etan was ever found. A civil court declared him dead in 2001.