Etan left home to walk to a school bus stop and was not seen again. In the early 1980s, his photo appeared on milk cartons across the country, the first time the method was used to try to locate missing children.
The boy's parents thought they would never find out what happened to their child, Stan Patz, Etan's father, said in a news conference on Tuesday.
"Now I know what the face of evil looks like and he's finally convicted," Patz said.
Hernandez was previously tried for the same charges in 2015, but was spared a conviction when a lone holdout on the jury led the judge to declare a mistrial
"We, as New Yorkers and as a community of families all over the United States, were also changed forever. Through this painful and utterly horrific real-life story, we came to realize how easily our children could disappear, ripped away from us right in our own neighborhoods" Manhattan District Attorney Cyrus Vance Jr. said in a statement.
Hernandez did not become a suspect until 2012. He confessed to police after authorities questioned him on a tip they received about the murder.
In a store basement, prosecutors said, Hernandez choked the boy to death and put his body in a plastic garbage bag that he concealed inside a cardboard box.
Hernandez, then a teenager, eventually left the box with other trash in an alley more than a block from the store.
His lawyers said he made up his account of the crime because of severe mental illness. Hernandez has been diagnosed with schizotypal personality disorder, one of a group of conditions informally thought of as "eccentric disorders."
Defense attorney Harvey Fishbein has long maintained his client has an "IQ in the borderline-to-mild mental retardation range" that made him susceptible to a false confession.
Etan's case raised awareness
Etan's remains have never been recovered.
Since their son's disappearance, the Patzes have worked to keep the case alive and to create awareness of missing children in the United States.
May 25, the anniversary of Etan's disappearance, is remembered as National Missing Children's Day.
"The abduction ... awakened the nation to child abduction and helped change the way law enforcement investigates these crimes," said John F. Clark, CEO and president of The National Center for Missing & Exploited Children.
"NCMEC is here today -- and America's children are safer -- because of Etan and other children whose abductions and killings launched a national movement."
The news industry was expanding to cable television, and sweet images of children appeared along with distraught parents begging for their safe return. The fear rising across the nation sparked awareness and prompted change from politicians and police.
In 1984, Congress passed the Missing Children's Assistance Act, which led to the creation of the National Center for Missing & Exploited Children.
President Ronald Reagan opened the center in a White House ceremony in 1984. It soon began operating a 24-hour toll-free hot line through which callers could report information about missing boys and girls.