The boys' mother played a part in cracking the case involving Autumn Pasquale, Gloucester County prosecutor Sean Dalton said at a news conference. She came forward with information about a posting on a son's Facebook account, leading police to the boys, Dalton said.
The girl appeared to have been strangled, he said. She had been riding her bicycle before she disappeared and was lured to the boys' house, where belongings including the bike were found, Dalton said.
Authorities did not discuss a motive. There were no signs of sexual assault, Dalton said.
The boys' names were not released because they are juveniles, but Dalton said his office is considering trying to have it transferred to adult court. The boys will have public defenders, but it wasn't clear yet who they were.
Both brothers were charged with counts including first-degree murder, body disposal and tampering with evidence. The 15-year-old was charged with luring.
Three teenage brothers live at the home where the body was found, said Na'eem Williams and Jodie Robinson, both 16. One of the teens in the home traded BMX bike parts, according to a young man, Corey Hewes, 19, who said he was among those who traded with him.
The house was a place where teens frequently hung out and had parties, some neighbors said.
Autumn's body was found around 10 p.m. Monday in the bin just blocks from her house and from Borough Hall, where thousands of people gathered earlier in the evening for a tearful candlelight vigil to pray for her safe return.
"The search for Autumn is over," Dalton said Tuesday. He called Clayton a safe community but said parents should continue to keep close watch on their children.
The girl's great-uncle, Paul Spadofora, thanked the community for its help in the search. The victim's parents did not attend.
"There's evil everywhere, even in the small town of Clayton," Spadofora said.
Crime scene investigators arrived shortly before 9 a.m. in the neighborhood where the body was found.
But Tuesday was trash collection day, and many residents had dragged their trash cans and recycling bins to the curb the night before. The covered recycling bins are collected by an automated truck that picks them up and dumps the contents into the back.
Police barricaded the block, and friends and neighbors came by to see. Some mothers said they were keeping their kids out of school for the day. Even before the body was found, students reported that Spirit Week had been canceled because of the sorrow.
One young man rode a bike up, sat on a porch of a home and cried, then biked away.
Clayton Mayor Thomas Bianco walked to the scene, cried, hugged a police officer and gave a brief statement to the gathered reporters.
"You hear about it in other places but never think it would happen in our little town," he said.
Autumn was last seen around 12:30 p.m. Saturday pedaling her bike away from the home where she lives with her father, her two siblings, her father's girlfriend and the girlfriend's children, authorities said.
Relatives said they believed she was heading to see a friend, and they became worried only after she did not return by her 8 p.m. curfew.
Sunday morning, her disappearance became not only a crisis but a town-wide cause in Clayton, a town 25 miles south of Philadelphia. Volunteers by the hundred joined the search, scouring malls, nearby towns and passing out fliers.
By Monday evening, officials were thanking the volunteers for their help but asking them to call it a night.
Hundreds of people returned Monday for the vigil. Spadofora, the great-uncle, said he hoped the town could gather again a week later, with Autumn back, with candles to mark her birthday.