"These were three young adults doing something positive for the community," state Police Maj. Walter Heesch said in a statement.
The crash was so violent that rescue workers had to cut off the roof to pull them out.
Killed were Jaime Malone, 22; Paige Malone, 19; and Michael Mulhall, 22, authorities said. Justine Mulhall and Kelly Murphy, both 20, were treated for minor injuries at Nassau University Medical Center. All the victims were from Floral Park.
They were driving on the Meadowbrook Parkway en route to Camp Anchor, a town-run seaside camp for about 600 adults and children with disabilities ranging from quadriplegia to autism to Down syndrome, said Hempstead Town Supervisor Kate Murray.
"We are all devastated by this tragedy," Murray said.
There's no doubt how special they were or how this accident has devastated the Floral Park community.
Hundreds crowded Our Lady of Victory for mass and hundreds more spilled onto the sidewalks on Thursday night.
Investigators were still trying to figure out exactly why the car veered off the highway.
"Alcohol involvement has been ruled out by State Police Investigators. Our prayers go out to the families in this tragedy, and also to the community of Floral Park, where all three of these young people were from," said Major Walter Heesch, Troop "L" Commander.
The six-week camp's name is an acronym for Answering the Needs of Citizens with Handicaps through Organized Recreation. It has one counselor for every camper, Murray said.
Officials restricted access to the camp in Lido Beach, on the southern shore of Long Island. They cited the need for privacy of both the campers and counselors, who Murray said were devastated. A police car was posted at the gate.
"As anybody who's ever come to Camp Anchor knows, the heart and soul of the camp are the young men and women who mostly volunteer and work with our campers," Murray told reporters outside the facility. "There is a very special bond that is life-enhancing both for the campers and the counselors."
Although many young people volunteer at the camp, the crash victims were paid employees who have worked with the summer program for three or four summers.
The campers had varying degrees of reaction, depending on their abilities, Murray said. But "they know that a big tragedy has happened today," she said.
(The Associated Press contributed to this report)