A 16-year-old male allegedly used a semi-automatic assault rifle to shoot to death his parents, sister and a family friend inside his parents' Long Branch home on New Year's Eve, according to Monmouth County Prosecutor Christopher J. Gramiccioni.

The teenager is in custody and is being charged with four counts of murder and possession of a weapon for an unlawful purpose, said Gramiccioni.

The victims were identified as the suspect's father, Steven Kologi, 44; mother Linda Kologi, 42; sister Brittany Kologi, 18; and family acquaintance, Mary Schultz, 70. They were found by police minutes after a 911 call of shots fired.

Gramiccioni said two other family members, the boy's grandfather and brother, were able to escape the house. Both were unharmed.

Gramiccioni said "thankfully (they) left the house," and we're "OK."

Gramiccioni said officials do not have a motive for what set the youth off on a murder spree.

The 911 call of shots fired was received by police at 11:43 p.m. from within the home at 635 Wall Street, Gramiccioni said.

A neighbor said he heard gunshots and fireworks from two different locations in the neighborhood go off almost simultaneously.

Investigators are shown outside the Wall Street home in Long Branch, NJ, Monday morning, January 1, 2018, where 4 family members were killed by a 16-year-old boy on New Year's Eve.

"I walked outside at midnight. We heard the commotion and lights flashing and saw (the police) storm the house," said James Roskowinski, referring to himself and a roommate.

Roskowinski, who is a resident on Wall Street, said he didn't know the family but felt bad upon learning the events of the tragedy.

"It's a shame the new year has to start off like this," said Roskowinski.

The suspect used a semi-automatic rifle to shoot his victims and was reportedly taken into custody without incident, said Gramiccioni.

The rifle was a Century Arms model, according to the Monmouth County Prosecutor.

One of the bodies is removed from a Wall Street home in Long Branch, NJ, Monday morning, January 1, 2018, where 4 family members were killed by a 16-year-old boy on New Year's Eve.

"The weapon was legally owned and registered to a family member," said Gramiccioni.

The four victims were pronounced dead at the scene. Gramiccioni said none of the victims were transported to a hospital.

The youth, who was not named by Gramiccioni, will most likely make his first appearance before a judge on Tuesday.

Because of the seriousness of the offense, Gramiccioni said the prosecutor could waive the youth out of juvenile court and try him as an adult, but no decision on that had been made as of Monday morning.

A joint investigation by the Monmouth County Prosecutor's Office and Long Branch Police Department continues.

The shooting was initially reported by the police over social media.

Gramiccioni said the incident is being treated as an isolated domestic incident and officials have "no reason to believe the public is at any risk."

Anyone with information about this case is asked to call Detective Andrea Tozzi, of the Monmouth County Prosecutor's Office at 800-533-7443, or Detective Michael Verdadiero of the Long Branch Police Department at 732-222-1000.

Dan Radel: 732-643-4072; dradel@gannettnj.com

Contributing Tom Costello.