NEWARK, New Jersey (CNN) -- Two people, including a 15-year-old boy, are in custody in connection with the execution-style slayings of three college students in a Newark, New Jersey, schoolyard, authorities said.
Jose Carranza, 28, of Newark, New Jersey, surrendered in the slayings of three college students.
Jose Carranza, 28, of Newark, surrendered with his lawyer at midday Thursday, Mayor Cory A. Booker said.
The suspect insisted on surrendering to the mayor after learning he was wanted for murder.
"He simply came forward. He said nothing," recalled Booker, who rushed from a news conference to meet the lawyer, Felix Lopez Montalvo, for the surrender. Watch Booker describe the surrender »
"We put him in handcuffs and we walked the individual into the office. I personally helped the detective to sit him down and I left," the mayor added.
The teenager was taken into custody at about 11 p.m. on Wednesday.
Booker said others are being sought. "We have very, very strong leads," he told reporters. "I want the killers off the streets of Newark."
Ballistics evidence, information from the shooting's lone survivor and a fingerprint lifted from a beer bottle at the scene led to the major break in a criminal case that has outraged a city numbed by street violence.
At a news conference earlier Thursday, Booker praised the "incredible courage" of survivor Natasha Aeriel, 19. She is in stable condition and under heavy police guard at The University Hospital in Newark, recovering from gunshot and knife wounds.
"From her hospital bed, she has been cooperating with authorities and making identifications," Booker said.
Newark Police Director Garry McCarthy and Essex County Prosecutor Paula Dow asked for the public's help in the rapidly developing case. A $150,000 reward is being offered for information.
An arrest warrant had sought Carranza's arrest for three counts of murder, a single count of attempted murder, four counts of robbery, conspiracy and weapons offenses.
"We believe that others were involved in this heinous crime. We are looking for them," Dow said.
The 15-year-old was not identified because of his age, but Dow said she would seek to try him as an adult.
Newark has become accustomed to violence but the slayings on Saturday night touched a nerve.
The four friends, ages 18 to 20, were shot while listening to music at the schoolyard.
Three of them -- Terrance Aeriel, 18, Dashon Harvey, 20; and Iofemi Hightower, 20 -- were forced to kneel against a wall and were shot in the head, execution style.
Authorities have said robbery appeared to be the motive, but Dow said Tuesday that police also were looking into possible gang involvement.
While Newark has seen 60 homicides this year, the schoolyard killings stood out because the victims, by all accounts, were good kids. All four were enrolled at Delaware State University or were in the process of enrolling.
James Harvey, Dashon's father, described his son Monday as "a good, good student, college student."
"For him to be killed on the streets of Newark needlessly is very unacceptable," he said at a news conference.
"They're out here hurting innocent kids," he added. "Innocent people are dying needlessly, unnecessarily and for what? For what? This has to stop." E-mail to a friend