20-year-old Justin Nojan Sullivan pled guilty on Tuesday morning to a chilling terrorist plot in which he planned to use a silenced gun to murder hundreds of people in Virginia and North Carolina on behalf of the Islamic State. He has agreed to serve a life sentence in prison.

“Justin Sullivan planned to kill hundreds of innocent people. He pledged his support to ISIL and took calculated steps to commit a murderous rampage to prove his allegiance to the terrorist organization,” said FBI Special Agent in Charge John A. Strong, of the Charlotte, North Carolina, office, as quoted by the Associated Press.

“Sullivan admitted in court today that he attempted to commit acts of terrorism transcending national boundaries by planning mass casualty shooting attacks on behalf of ISIL against innocent people in North Carolina and Virginia,” stated U.S. Attorney Jill Westmoreland Rose.

“It is frightening to know that the defendant in this case was able to use social media to contact and seek advice from ISIL, a murderous organization,” Rose added.

More specifically, Sullivan planned to attack a concert, nightclub, or other crowded venue, where he thought he might be able to kill up to a thousand people. He was planning to film the slaughter and give the video to ISIS. He also proposed pulling off a few “minor assassinations” for training purposes before carrying out “the big attack.”

Sullivan admitted to being in “frequent and direct communications” with ISIS recruiter Junaid Hussain in the summer of 2015. He also began communicating on social media with people who turned out to be undercover FBI agents. Hussain was killed by a U.S. drone strike in Syria in August of 2015.

According to court documents cited by Reuters, Sullivan was also a consumer of ISIS murder videos and a convert to Islam. His father reported him to the FBI after he destroyed some religious items in the family home.

“I liked IS from the beginning then I started thinking about death and stuff so I became Muslim,” he told the undercover agent.

Sullivan went so far as to ask his FBI correspondent to build him a silencer and then offered to pay for the murder of his parents after his mother discovered the silencer and asked questions about it.

He reportedly planned to carry out his massacre while his parents were away from the house but was arrested by FBI agents in June 2015 before he could act.

Reuters reports that Sullivan has also been accused of murdering his elderly neighbor, John Bailey Clark, using a .22-caliber rifle he stole from his stepfather. Clark was found buried in a shallow grave behind his house, with three gunshot wounds to the head.

Sullivan said he robbed Clark of $689, which he intended to use for the purchase of an AR-15 rifle and ammo for his shooting spree, but he has not formally confessed to Clark’s murder. The FBI found the stolen .22 rifle, along with some muddy clothes, a black ski mask, and a lock pick kit, hidden in the crawlspace of the Sullivan family home when they arrested him.