The crash happened around 3 p.m. in the eastbound lanes near the Hammonton Exit in Atlantic County.
New Jersey State Police say the driver lost control, sending the car into the woods.
That driver, who survived with moderate injuries, is identified as 19-year-old Nijul Crawford.
Killed in the crash were two brothers, 15-year-old Emmanuel Crawford and 16-year-old Marcus Crawford, both of Camden, along with 19-year-old Maryha Toro of Philadelphia.
Marcus and Emmanuel were Pennsauken High School students. Marcus, who was about to start his junior year, was in the electrical program and ran track, while Emmanuel - known as "Manny" - was about to enter his sophomore year. He played basketball and football.
"It's a very large family - the mom actually works in the district also. They are a great family they are very personable, they were helping out with the school community, they were part of Pennsauken," said Principal Richard Bonkowski.
During a graduation ceremony on Monday night, seniors paused to remember Emmanuel and Marcus.
The school says the Crawfords' sister was to receive her high school diploma Monday night. Instead, she and her family are grieving.
"She's being there for her mom, which is most important because her mom is really going through it, but she's staying strong for her," said graduating senior Evelyn Cortorreal, who is also a family friend.
Toro was the girlfriend of Nijul Crawford. She was a recent graduate of Excel High School.
"She was a very sweet girl, very intelligent, she was just wonderful," said grandmother Miriam Perez. Toro's family plans to hold a vigil for her on Monday night.
The family was headed to the shore in multiple vehicles when the crash occurred.
Crash on Atlantic City Expressway under investigation