A man who plotted to shoot hundreds of people on behalf of the Islamic State group received a life sentence Tuesday.

Justin Nojan Sullivan, 21, of North Carolina received the sentence in federal court in Asheville after pleading guilty late last year to the foiled plot to attack a nightclub or concert and film it for distribution on terrorist sites.

Prosecutors say Sullivan's case illustrates the dangers of Americans radicalized through social media.

Justin Nojan Sullivan, 21, received a life sentence for his plot to kill hundreds

Sullivan was a teenager in the small foothills town of Morganton when he became radicalized in 2014 after watching terrorist beheadings and other Islamic State propaganda online, US Attorney Jill Westmoreland Rose said Tuesday

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

It was a Rich's call that alerted authorities to his son’s possible ties to the Islamic State, a worldwide terrorist group commonly known as ISIS or ISIL.

Sullivan was arrested at his family home in June 2015 after his father called 911 because he was destroying religious items in their house

Sullivan still faces state murder charges in the death of his neighbor John Bailey Clarke, who was killed in his sleep. Sullivan allegedly took the man's money afterwards to fund his terror plot

A few months later, Justin Sullivan offered to pay an undercover FBI agent posing as an ISIS sympathizer to have his parents killed out of fear that they would thwart his plans.

Authorities say Sullivan admitted to having frequent contact online with a prominent Islamic State recruiter and propagandist in Syria, the now-dead Junaid Hussain.

Sullivan agreed to Hussain's request to make a video of his planned attack so that it could be used online for recruitment, Rose said.

'They know this is a way to win the hearts and minds of American youth or those who may be disenfranchised in some way,' Rose told reporters after the sentencing hearing.

'Certainly the use of social media by foreign terrorist organizations, particularly ISIS, is one of the ways that they're most effective.' ISIS is an alternative acronym for the Islamic State group.

Sullivan, who was arrested at his parents' house in June 2015, planned to buy a semi-automatic rifle at a gun show to kill hundreds of people at a concert or night club near where he lived in western North Carolina, Rose said.

She said he planned to use an AR-15 rifle and hollow-point ammunition 'because he knew that he could inflict mass casualties and mass pain.' She described his plan as 'a murderous plot that was serious and imminent.'

The suspect discussed his plans on social media with an undercover FBI employee who Sullivan believed to be sympathetic to his views, and he tried to recruit the person to help.

After his mother discovered a silencer that was mailed to Sullivan, he offered the undercover FBI employee money to kill her and his father so they wouldn't interfere, according to court documents.

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

Authorities say Sullivan expressed his support for the Islamic State in front of his parents and smashed religious objects in their home. Rose said Sullivan's father, a military veteran, contacted authorities, who were already monitoring the son.

Sullivan also faces a state murder charge after authorities say he took a rifle from his father's gun cabinet and killed a 74-year-old neighbor, John Bailey Clarke, with it in December 2014. He took the man's money to use for his terror plot, according to court documents.

Sullivan pleaded guilty in federal court late last year to one count of attempting to commit terrorism.

Yet Sullivan told a federal judge during Tuesday's hearing that he's not a 'cold-blooded murderer.' Asked afterward about Sullivan's statement, Rose responded: 'I think the facts would show otherwise.'