Justin Nojan Sullivan, 20, pleaded guilty in federal court in North Carolina on Tuesday after he plotted to carry out a terrorism attack at a concert or club where he believed as many as 1,000 people would die

A North Carolina man who plotted U.S. terror attacks with a member of the Islamic State group has pleaded guilty to terrorism.

Justin Nojan Sullivan, 20, pleaded guilty in federal court in Asheville on Tuesday to one count of attempting to commit an act of terrorism transcending national boundaries.

He planned an attack at a concert, bar or club where he believed as many as 1,000 people would die, according to federal officials.

'Justin Sullivan planned to kill hundreds of innocent people,' said John A. Strong, a special agent in charge of the FBI's office in Charlotte.

'He pledged his support to ISIL and took calculated steps to commit a murderous rampage to prove his allegiance to the terrorist organization.'

Sullivan said in court that he planned shootings in North Carolina and Virginia that would cause mass casualties, according to U.S. Attorney Jill Westmoreland Rose.

He also claimed he had 'frequent and direct communications' with Junaid Hussain - an Islamic State member who asked him to make a video of the attack.

Hussain, who was responsible for online recruitment and providing inspiration for attacks in Western countries, began conspiring with Sullivan by June 2015.

The 20-year-old pleaded guilty on Tuesday to one count of attempting to commit an act of terrorism transcending national boundaries

Authorities say Sullivan had been in contact with ISIS recruiter Junaid Hussain who had asked him to film the attack. Hussain was killed in a U.S. drone strike in Syria in August 2015

Hussain was killed in a U.S. drone strike in Syria in August 2015.

But then Sullivan discussed those plans on social media with an undercover FBI employee, whom Sullivan tried to recruit to participate in the attacks, according to authorities.

He asked the undercover FBI employee to build silencers and told him that he planned to carry out his attack in the next few days.

Federal authorities have said they began investigating Sullivan after his father called 911 in April 2015 saying his son was destroying religious items in their home.

He was arrested at the family's home without incident on June 19, and later told investigators that he planned to carry out an attack in the coming days when his parents were expected to be out of town.

Sullivan was arrested at his family home in June last year after his father called 911 because he was destroying religious items in their house

He also had offered to pay the undercover employee for killing his parents, who he believed would interfere with his terrorism plans.

A sentencing hearing hasn't been scheduled, although both sides agree a life sentence is appropriate.

Sullivan also faces state charges in the death of his neighbor, John Bailey Clark, who was killed in December 2014.

At the hearing Tuesday, he didn't say he had killed Clark; however, prosecutors reserved the right to prove the charge at the sentencing hearing.