All were from Newark and planned to attend Delaware State University this fall.
Essex County Prosecutor Paula Dow said authorities didn't have any suspects or a motive in the killings late Saturday. None of the victims had any criminal record, she said.
"They were good kids," Dow said.
The four had been listening to music in a parking lot behind Mount Vernon School when they were gradually joined by a group of men, authorities said.
Newark Police Director Garry McCarthy said the four exchanged text messages saying they should leave, but were attacked before they could do so.
Police said the attackers shot one young woman, then forced her three companions down an alley, lined them up against a wall, made them kneel and shot each in the head.
Natasha Aerial, 19, was listed in fair condition at Newark's University Hospital, authorities said. Police identified her companions as her brother, Terrance Aerial, 18, Iofemi Hightower, 20, and Dashon Harvey, 20.
The Aerials' mother, Renee Tucker, said the last time she saw them was around 10:30 p.m. Saturday, when they told her they were going around the corner to get something to eat.
"They said they were going to come right back to the house," Tucker said.
Iofema Hightower's family sought comfort Monday at the lonely place where she was shot to death, reports CBS News correspondent Michelle Miller. They prayed for peace and hoped for answers.
Hightower was a motivated student who had recently enrolled at Delaware State, according to his great-uncle, John McClain.
"She was one of the most beautiful ladies you'd ever want to meet," McClain said. "Very smart, very intelligent. She wanted to be something in life."
As WCBS' Magee Hickey reports, according to Newark Mayor Corey Booker, the victims were Newark's success stories: hard-working students who never had any run-ins with the law. "This breaks the heart of our city. This is something that is really a blow to every resident of this city. We must come together," Booker said.
But a group called Take Back Our Streets is holding Booker accountable for the shootings, and is planning a rally at City Hall to demand his resignation.
"The rally today is to get better policing and better protection up here because this neighborhood is under siege. A lot of car robberies, break-ins, muggings and everything up here," said demonstrator Frank Bristol.
Still, Newark's homicide total is down from this time last year, when the murder count was at 63, and many feel Booker has done a good job as mayor.
A month ago, Booker and Police Director Garry McCarthy announced that crime in the city had fallen by 20 percent in the first six months of 2007 compared with a year ago. Yet despite decreases in the number of rapes, aggravated assaults and robberies, the killings have continued.
"He doesn't deserve another day, another second, while our children are at stake," said Donna Jackson, president of Take Back Our Streets, a community-based organization. "Anyone who has children in the city is in panic mode."
Booker's office didn't return a call for comment on Monday.
Saturday night's killings, along with an unrelated shooting over the weekend that killed a Montclair man, brought Newark's 2007 homicide toll to 60. That is three fewer than in the same period in 2006. But there have been 17 slayings in the eight weeks since June 12.
Officials at Delaware State said the school plans to hold a memorial service Aug. 28, after the student body returns for the fall semester.
"While the murder of the two students is a terribly loss in human terms, the facts that they were a part of the DSU family and were striving to earn a degree, create a bright future for themselves and become a solid contributors to society, makes this violent act especially tragic and senseless," university president Allen Sessoms said.