NEW YORK (Reuters) - A New York City college student died last November fighting for Islamic State in Syria, where he had traveled earlier in the year with the assistance of an Arizona man he met online, according to U.S. prosecutors.

The death of Samy Mohammed El-Goarany, who was 24 when he traveled to Syria, was disclosed in papers filed by prosecutors late on Monday in Manhattan federal court in a case against the Arizona man, Ahmed Mohammed El Gammal.

The details came as prosecutors sought approval to introduce evidence at the Dec. 5 trial of El Gammal, who is charged with conspiring to provide material support to Islamic State by helping El-Goarany travel so he could join the militant group.

The potential evidence includes a letter by El-Goarany that an unidentified person via an instant messaging platform provided one of El-Goarany’s relatives after saying he had been killed fighting in Syria.

In the letter, El-Goarany informed the relative that “if you’re reading this then know that I’ve been killed in battle and am now with our Lord InshaAllah.”

“We will win this war one day, this war between Iman (Belief) and kufr (Disbelief) between Good and Evil,” the letter said, according to prosecutors. “And I will come back for you, with Allah’s permission I will come back for you.”

El Gammal’s lawyer declined comment. He has pleaded not guilty.

According to prosecutors, El-Goarany was a U.S. citizen who attended college in Manhattan and who by 2014 began expressing increased interest in militant forms of Islam.

El-Goarany first contacted El Gammal in August 2014 after learning of online comments he posted supporting Islamic State, prosecutors said.

They corresponded via encrypted messaging platforms, including one El-Goarany recommended by noting former National Security Agency contractor-turned-whistleblower Edward Snowden had used it, prosecutors said.

They said El Gammal traveled to New York in October 2014 and met El-Goarany. He then arranged for El-Goarany to get in touch with an individual living in Turkey to help El-Goarany travel to join Islamic State, prosecutors said.

El-Goarany, whose parents lived in Middletown, New York, subsequently traveled from New York City to Istanbul in January 2015, and sometime in mid-February arrived in Syria, prosecutors said.

After learning of El Gammal’s August 2015 arrest, El-Goarany posted a video on YouTube denying he had helped him and saying he “came here out of my own will,” prosecutors said.