WASHINGTON, Jan. 1 (Xinhua) -- Fifteen minutes before the arrival of the year 2018, shots fired at a home in northeastern U.S. state of New Jersey, leaving four people dead and a 16-year-old boy in jail.

Among the dead were the boy's parents and 18-year-old sister, Monmouth County Prosecutor's Office said in a news release on Monday.

The fourth dead is a 70-year-old person who lived with the family.

Investigators believe a "Century Arms semiautomatic rifle" was used in the deadly shooting, according to the new release.

It's unclear whether anyone else was in the house at the time of the shooting. The motive of the killing is also under investigation.