SANTA ANA, Calif. - A California man who aspired to join the Islamic State of Iraq and Syria (ISIS) in Syria and lied to get a replacement American passport to head overseas was sentenced Monday to 15 years in prison and supervised release for life.

The case against Adam Dandach, 22, is one in a series involving young men and women in states ranging from California to Georgia who have been charged with trying to assist ISIS and other terrorist groups.

Dandach, an Orange County native, pleaded guilty last year to attempting to provide material support to a terror group and lying on his passport application. Federal prosecutors had sought a 20-year sentence.

The U.S. "faces significant threat from terrorists' acts planned or committed by homegrown violent extremists like (the) defendant who become radicalized online and seek to engage in terror and support groups like ISIL," federal prosecutors wrote in court filings, using an alternative acronym for ISIS.

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Before ordering the sentence, U.S. District Judge James V. Selna in Santa Ana called Dandach's conduct "serious" and said terrorist activity in any form is a threat to the United States and other countries.

The thin Dandach appeared in court wearing shackles and a tan jail jumpsuit and said he had dissociated himself from the person he used to be.

"Pardon me for my poor judgment," he told the court. "I believe it should be understood that I am just a hollow shell of what I used to be."

Dandach's mother sobbed in the courtroom during the hearing.

Dandach had praised terrorists and promoted their lectures and videos online before planning to go to Syria, federal prosecutors wrote.

After Dandach's mother took his passport to keep him from traveling to Syria, CBS Los Angeles reports. He lied to get a replacement - saying he had accidentally tossed out his old passport - then booked a trip for July 2014.

He was stopped at John Wayne Airport by FBI agents who found his smartphone loaded with jihadi songs supporting ISIS fighters, maps of areas the group controlled, and Twitter updates on fighting by the terrorist group.

Prosecutors say Dandach told the agents he planned to pledge allegiance to the Islamic State and train with weapons to defend himself.

In court papers, defense lawyer Pal Lengyel-Leahu wrote that his client had been treated for a spate of psychological problems including depression and post-traumatic stress disorder after suffering an abusive childhood.

The judge said Dandach's mental health should be taken into account in his sentence.

Dandach found a purpose to his life in religion and aimed to travel to a place where people professed those beliefs, the lawyer wrote. He added that Dandach never planned any terrorist acts and that his client claimed Islamic State was not a designated terrorist group when he planned his trip to Syria to join a charitable aid convoy in 2013.

Lengyel-Leahu said after the hearing that he thought the sentence was harsh.

The judge "looked at the case and he treated Adam as if he were like every other travel case," he told reporters.

Prosecutor Celeste Corlett declined immediate comment.