A US court had charged a teenager with attempt to support the Islamic State (IS) terror group, a media report said on Tuesday.
The teenager from North Carolina state has also been charged with planning fatal shootings and bomb attack in the country.
Justin Sullivan, 19, was charged on Monday for terror offences and possession of weapons, reported USA Today.
He had in possession an illegal silencer.
According to the federal court, Sullivan was arrested on June 19, after he told the undercover agent his plans of obtaining a rifle from a gun show in a neighbouring suburb "which he planned to use to kill a large number of US citizens on behalf of IS."
On June 6, a Federal Bureau of Investigation (FBI) undercover agent made initial contact with Sullivan who allegedly described himself as a "mujahid" (warrior), adding that the "war is here".
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Sullivan indicated that a toll of 1,000 was the goal.
In the shootings, which he wanted to launch this month, Sullivan discussed using ammunition coated with cyanide.
"And then set off a gas bomb to finish the rest," he allegedly told the agent.
In conversations with the agent, Sullivan repeatedly discussed his "anger" with US-led air-strikes against IS fighters in Iraq and Syria, and said he wanted to act "sooner".
If convicted, Sullivan faces a maximum punishment of 20 years in prison and a $250,000 fine for each charge.