Nineteen-year-old Chicago resident Mohammed Hamzah Khan was charged with attempting to provide material support to a foreign terrorist organization today after getting arrested Saturday at the O'Hare airport. FBI agents say Khan planned to go overseas and fight with ISIS in Iraq or Syria.

According to NBC Chicago, Khan purchased a roundtrip ticked to Istanbul on September 26. He allegedly planned to go to Syria or Iraq from there. The FBI searched his house and found "multiple handwritten documents that appeared to be drafted by Khan and/or others, which expressed support for ISIL," including a letter to his parents.

In the letter, according to the FBI, Khan explained his plans and invited his family to join him. "First and foremost, please make sure to not tell the authorities for if this were to happen it will jeopardize not only the safety of us but our family as well," he wrote.

Khan isn't the first American teen to be arrested at the airport while trying to get to ISIS. Colorado teen Shannon Maureen Conley pleaded guilty to providing material support to a terrorist organization last month after falling in love with an ISIS militant online and attempting to join him in Syria.

[Photo via AP]