Updated

A northern New Jersey teenager has appeared in court to face charges that he fatally stabbed his 20-year-old sister with a kitchen knife during an argument.

Bergen County Prosecutor John Molinelli says the 17-year-old suspect stabbed his sister Teia (TEE'-uh) Gallo multiple times around 5:30 p.m. Thursday in their Washington Township home.

Friday's court hearing in Hackensack was closed because the suspect is a juvenile. A public defender entered a not guilty plea. Prosecutors say they will decide within the next month whether to have the suspect tried as an adult.

Officials say the suspect and victim are among 12 children in the family. The prosecutor says another sibling was home at the time of the stabbing and called 911. The Gallo family had nine biological children before deciding to adopt the suspect, victim and victim's sister.

"We're a very strong family," Dr. Robert James Gallo, the family's patriarch told NorthJersey.com. "There's a lot of love and a lot of hugging, and we will get through this. We will weather this storm," Gallo told the news station.

A friend of the victim told the news station that Teia was looking to get away from the suspect who she described as "aggressive."

"She wanted to live on campus next year to get away from his anger," Jennifer O'Connor, a friend of Teia's told NorthJersey.com. Teia was reportedly a junior at Dominican College but was living at home.

A neighbor described the suspect as a "normal kid," though quiet.

Gallo reportedly said he noticed no change in his son's behavior leading up to the stabbing.

"She was a loving kid. She was adored by my grandchildren, by her sisters and brothers," Gallo told NorthJersey.com. "She will be sorely missed," he said.

The Gallo family's spacious, well-kept house sits at the end of a cul-de-sac in a quiet residential neighborhood.

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The Associated Press contributed to this report.