Columbus - A Somalia-born man living in the US travelled to Syria and trained alongside terrorists, then returned with plans to attack a military base or a prison, according to a federal indictment announced on Thursday.Abdirahman Sheik Mohamud, a US citizen originally from Somalia, wanted to "kill three or four American soldiers execution style", according to the indictment. Attacking the prison was part of a backup plan if that didn't work, the charges said.The indictment also says Mohamud's brother, Abdifatah Aden, fought with Jabhat al-Nusrah, a state department-designated terrorist group, until he was killed in battle in Syria in June 2014.Mohamud, 23, of Columbus was charged with supporting terrorism, supporting the same terrorist group and making a false statement involving international terrorism when he allegedly lied to an Ohio FBI agent by saying he was in Istanbul when authorities say he was in Syria.Unnamed associatesThe government charged Mohamud under the laws most commonly used since the 11 September attacks to prosecute terror suspects. He faces up to 38 years in prison if convicted.Mohamud was arrested in Columbus in February on state terrorism and money laundering counts. Thursday's charges were expected, and Mohamud will plead not guilty at a Friday arraignment, said his attorney, Sam Shamansky. He said it was too early to talk about the specific charges.Mohamud became a US citizen in February 2014, according to the government.The government didn't say how it learned of the plot, but the indictment mentions two "unnamed" associates of Mohamud in the US to whom he gave information about his activities, including a video of Mohamud carrying an AK-47.One of them said he believed Mohamud was trying to recruit him to participate in the plot, according to the indictment. The government also said Mohamud made terrorism-related Facebook posts in 2013.US Representative Michael McCaul, chairman of the Committee on Homeland Security, said the charges highlight the threat posed by Americans joining extremists overseas then returning home.Shooting weaponsEvents leading to Mohamud's arrest began around September 2013 when he communicated online with his brother over plans to also travel to Syria to fight, the indictment said. They later talked about ways Mohamud could support him financially, according to the government.Mohamud told his brother of his desire to "join you in the high ranks as a Mujahid," or violent jihadist, according to the indictment.Mohamud also told one his US associates he was happy about his brother's death and said he "was next and would join Aden soon," the indictment said.A year ago, Mohamud bought a one-way plane ticket to Athens with a connection in Istanbul, where he got off and didn't board his next flight, the indictment said. Instead, he ended up in Syria where he received training "including shooting weapons, breaking into houses, explosives, and hand-to-hand combat," the government said. A cleric then instructed him to return to the US to carry out an act of terrorism, according to the government.In 2012, a Somali immigrant to Columbus who federal prosecutors say plotted to attack a shopping mall was deported to Somalia.Thursday's indictment is one of several recent cases involving people in the US, including citizens, accused of travelling overseas to fight in Syria.