Prosecutors say Elvis Redzepagic was removed from his home in Commack last week after he tried to cut off his own tattoos with a knife and threatened to behead his mother.
The allegation was included in documents prosecutors submitted to a federal judge opposing bail for the 26-year-old Redzepagic, who was charged Saturday with attempting to provide material support to a foreign terrorist organization. His lawyer, Mildred Whalen, noted that Redzepagic is a citizen and had cooperated with law enforcement. She says her client needs counseling.
"We will be working with his family in the hope that the court and the government will see that what he needs is counseling and support, not imprisonment," she said in an email.
The defense did not submit for bail and are said to still be preparing a bail package. The judge granted a permanent order of detention.
Prosecutors say Redzepagic is originally from Montenegro, in the Balkans.
He is being held on terrorism charges after federal authorities said he was prepared to strap on a bomb and sacrifice himself for jihad and persistently tried to join extremist groups in Syria.
He was arrested on Long Island February 2 on an unrelated charge and reportedly told police "I'm going to leave this country, and I'm going to come back with an Army - Islam is coming," according to a federal court complaint.
Authorities have prosecuted a number of people accused of trying to join the Islamic State group and other militants in recent years, though in some cases, the accused haven't actually succeeded in traveling overseas.
Redzepagic "was persistent in his efforts" to join Islamic militants in civil-war-ravaged Syria, making it to Turkey in 2015 and Jordan last year and even getting to the Syrian border, said William F. Sweeney, assistant director in charge of the FBI's New York field office.
(The Associated Press contributed to this report.)