— A North Carolina man accused of planning an Islamic State-inspired attack has also been charged with killing his neighbor.

District Attorney David Learner said a grand jury in Burke County indicted Justin Nojan Sullivan, 19, on Monday on a murder charge.

A federal indictment unsealed Monday charges Sullivan with attempting to provide material support to the Islamic State, as well as firearms offenses, charges that he lied to federal agents and a count related to offering to pay an informant to kill his parents.

Prosecutors say Sullivan admitted to taking a rifle from his father's gun cabinet and that testing showed the gun killed his 74-year-old neighbor, John Bailey Clark, in December 2014. The indictment alleges he later hid the gun, along with an illegal silencer he obtained and other items in the crawl space of his parents' home in Morganton and that he stole $689 from Clark and intended to use it to buy an assault rifle and ammunition.

An attorney for Sullivan declined to comment.

Sullivan's father tipped off authorities to his son's activities.

"Warning signs were there, and that's why I made some calls," Rich Sullivan said. "I can never forgive him for what he planned or condone it. I'm a retired Marine, but we have to love him.

"You have to watch your children," he continued. "Even if you do watch them, you think they're safe at home, (but) they're not."

Sullivan was arrested over the summer and accused of planning terrorist killings in the U.S. He's in federal custody awaiting trial.