(Reuters) – A North Carolina man was indicted on Monday in the murder of a 74-year-old neighbor police said he killed months before federal authorities arrested him on allegations that he planned mass shootings to support Islamic State militants.

Justin Nojan Sullivan, 19, of Morganton, North Carolina, is charged with murder in the December 2014 slaying of John Bailey Clark, said Burke County District Attorney David Learner.

Sullivan also faces seven federal charges related to supporting Islamic State and plotting murders, according to an 11-page federal indictment unsealed Monday. He faces trial on those charges later this month.

Islamic State is a militant group that controls parts of Syria and Iraq and has vowed attacks on the West.

“Justin Sullivan had elaborate plans to kill hundreds of innocent people to show his support for the terrorist organization, ISIL,” said FBI Special Agent in Charge John A. Strong.

The first-degree state murder charge is punishable by life in prison without parole or the death penalty.

The federal charges range in punishment from 20 years in prison for attempting help Islamic State to eight years for lying to a federal agency.

Attorneys for Sullivan could not be reached.

The FBI began tracking Sullivan in September 2014 after his parents, with whom he was living, told police he supported Islamic State and was destroying Buddhist objects at home.

In December, 2014, Clark was killed with the .22-caliber rifle later identified as one that Sullivan stole from his father and hid under their house, according to the indictment.

Beginning on June 6, 2015, Sullivan began talking about his Islamic State loyalties with an undercover federal agent Sullivan took for a fellow supporter.

“I liked IS from the beginning then I started thinking about death and stuff so I became Muslim,” Sullivan told the agent, according to the indictment.

Over the next two weeks, Sullivan told the agent that he wanted to kill hundreds or thousands with an assault rifle and silencer, and planned to practice killing with minor assassinations, the indictment said.

He instructed the agent to obtain weapons, had the agent make and mail him a silencer to use, planned to buy an AR-15 at a gun show and tried to buy hollow-point bullets.

When his parents questioned him about the silencer, he tried to hire the agent to kill them, the indictment said.

He was arrested in late June 2015 and remains in federal custody, authorities said.

(Reporting by Letitia Stein and Karen Brooks; Editing by David Gregorio)