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 .
NEW : Jose Carranza , 28 , surrenders in schoolyard shootings case . NEW : Boy , 15 , taken into custody Wednesday night . College students forced to kneel against wall , shot in head . Slayings shocked Newark , New Jersey , where street violence is common .