Three friends were forced to kneel against a wall behind an elementary school and were shot to death at close range, and a fourth was found about 30 feet away with gunshot and knife wounds to her head, police said.
All were from Newark and planned to attend Delaware State University this fall.
Paul Loriquet, a spokesman for the Essex County Prosecutor's office, said Monday no arrests had been made and authorities had not identified suspects. Mayor Cory A. Booker was scheduled to hold a news conference at 1:30 p.m.
None of the victims had criminal records, authorities said.
"They were good kids," Essex County Prosecutor Paul 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 indicating they sensed trouble and believed 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.
In the wake of the killings, Booker again found himself defending his administration's inability to make a dent in the city's alarming murder rate.
"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. It takes something like this for people to open up their eyes and understand that not every person killed in Newark is a drug dealer."
Booker's office didn't immediately return a call for comment on Monday.
On Monday, Booker spoke to children at the school, which sits in a middle-class neighborhood about a quarter-mile from the campus of Seton Hall University.
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 to a year ago. Yet despite decreases in the number of rapes, aggravated assaults and robberies, the murders have continued at an alarming rate.
Saturday night's killings, along with an unrelated shooting over the weekend that killed a Montclair man, brought Newark's murder total to 60 in 2007.
That is three fewer than in the same period in 2006. But that statistic obscures a more disturbing one: 17 people have been killed in the city in the eight weeks since June 12, a rate that would surpass 2006's total of 106 murders for the calendar year.
Harvey's page on MySpace.com was filled with messages from friends on Monday. On the page, Harvey described himself as a sometime runway model whose heroes were Superman and Martin Luther King "and last but not least, My DAD," and who planned to graduate from Delaware State in 2009 with a degree in psychology.
Hightower was a motivated student who had recently enrolled at Delaware State, according to 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."
At Delaware State, officials said the school plans to hold a memorial service Aug. 28, after the student body returns for the fall semester.
"We are deeply saddened over the violent shooting incident that took the lives of two of our students and left one seriously injured," university President Allen Sessoms said in a statement. "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."