A Colorado teenager has been arrested for trying to join ISIS, the Justice Department said on Tuesday. Humzah Mashkoor was arrested by the FBI after allegedly attempting to board a flight in Denver to join ISIS, the Justice Department said in a criminal complaint. His arrest came just under a year after the FBI first encountered the teenager on social media when he was 16-years-old following a tip-off they received from the unidentified platform. Undercover FBI agents then began communicating with Mr Mashkoor, who used the social media name “Humzah Afghan,” the complaint said, and shared videos online of people getting executed. “Mashkoor frequently expressed support for ISIS,” the complaint reads. The teenager allegedly told an undercover FBI agent he and his family went to Afghanistan and then came back to the US, where he was born, after his family had to leave. “He indicated a desire to return to Afghanistan, where he has family in Nangarhar and other areas under Taliban control,” the complaint said. The Justice Department added that Mr Mashkoor stated that he “previously supported the Taliban but started ‘looking more into’ ‘the dawla’ after they ‘b0mbed the airport and took those Taliban and US soldiers and sent them to jahanam,’” the Justice Department said in the complaint. Authorities said they took his statements to mean he supported ISIS after the bombing of Kabul Airport in 2021. “Are you ready?” he allegedly wrote to an undercover FBI agent regarding his planned return to Afghanistan. “Once we go there’s no turning back… We leave behind everything… Our family’s… Our homes… Our friends… For the sake of Allah. … Life won’t be easy, we will be strangers moving from place to place… Hated by the whole worlds.” The complaint added that the teenager had allegedly told undercover officers he would do anything ISIS told him to do in the fall of 2022. “I am prepared to do anything which they require me to do . . . I just want to be used as soon as possible, gun attcks … I have no training, I used to have some practice with guns with I was younger. But that is it,” Mr Mashkoor allegedly said. Also, according to the complaint, in October 2022, he allegedly took the oath to join ISIS. The Justice Department further alleged that leading up to his 18th birthday, Mr Mashkoor made statements about traveling to join ISIS and allegedly discussed marrying someone who shared the same beliefs.He also allegedly planned to donate “all of his money” to ISIS in cryptocurrency before he turned 18. Mr Mashkoor planned to travel to Afghanistan on 11 December, but had to postpone his trip and was arrested on 18 December, the day of his rescheduled trip. The 18-year-old is not the first US teenager to be arrested after allegedly attempting to join ISIS. In 2014, three teenage girls from the Denver suburbs were arrested in Germany allegedly trying to fly to Turkey. According to CNN, investigators in the case believe the girls may have been trying to join a wave of foreigners from dozens of nations who have used Turkey as a route into Syria to fight with ISIS. The three girls were taken back to their families before being questioned and released by the FBI.