CHARLOTTE, N.C. — A 19-year-old North Carolina man is in federal custody after telling an undercover FBI employee that he wanted to support the Islamic State group by killing as many as 1,000 people in the United States, authorities said Monday.

Justin Nojan Sullivan of Morganton faces several charges, including one count of attempting to provide material support to the Islamic State group.

Sullivan “was planning assassinations and violent attacks in the United States,” said Assistant Attorney General for National Security John P. Carlin.

According to the criminal complaint, Sullivan planned to buy a semi-automatic AR-15 rifle on June 20 at the Hickory Gun Show so that he could kill as many as 1,000 people and demonstrate his support of the Islamic State group.

Federal authorities began investigating Sullivan after his father told emergency dispatchers on April 21 that his son was destroying religious items in their home. “I don’t know if it is ISIS or what, but he is destroying Buddhas and figurines and stuff,” the complaint quotes Sullivan’s father as telling 911.

An undercover FBI employee who first made contact with Sullivan on June 6 said Sullivan described himself as a Muslim convert. Two days later, he said he wanted to kill 500 people but the next day said he wanted to kill 1,000 by using biological weapons, bullets coated with cyanide and a gas bomb.

He suggested doing “minor assassinations before the big attack for training.”

On June 9, the complaint says Sullivan asked the undercover employee to build a firearms noise suppressor for him. The suppressor was delivered June 19 to Sullivan’s home, the complaint says.

After that delivery, the FBI searched the home and found the silencer under plastic in a crawl space accessible from the basement, the complaint says.

It appears that Sullivan may have given conflicting statements to his interrogators.

In an interview with the FBI, Sullivan said didn’t intend to carry out the plans, the complaint says. But he also said he intended to conduct the attacks between June 21 and June 23 because his parents would be out of town. He said he had asked the undercover employee to kill his parents.

Sullivan, who also is charged two counts involving possession of a silencer, was arrested Friday at his home without incident. He made his initial appearance Monday in federal court in Charlotte, where he answered questions from a U.S. magistrate judge, according to media outlets. It wasn’t immediately known whether he had an attorney who could be contacted for comment on the case.

The next hearing is scheduled for Wednesday morning at the federal courthouse in Asheville.

The Islamic State group is a militant organization that broke with the al-Qaida network and took control of large parts of Iraq and Syria, where it declared a caliphate, a traditional form of Islamic rule. It is made up of mostly of Sunni militants from Iraq and Syria, while also drawing jihadi fighters from across the Muslim world and Europe.

First Published June 22, 2015, 7:29 p.m.