A naturalized U.S. citizen has been charged with terrorism charges for plotting attacks within the U.S.

The man had traveled to Syria and trained with the Nusra Front, al-Qaeda's affiliate in Syria. He was caught before he could carry out the attack.

Abdirahman Sheik Mohamud, 23, a citizen born in Somalia, was arraigned on April 17 on federal terrorism charges for plotting attacks against American citizens and troops, according to CBS News. These attacks included an assault on military base in Texas or an attack against a prison.

Unlike other homegrown terrorists, who are radicalized online and plan attacks independently, Mohamud traveled last year to Syria where he met up with the Nusra Front and was training in various offensive skills, including the making of explosives.

But, instead of being sent to the front, he was instructed to return to the U.S. and conduct an attack.

According to the New York Times, Mohamud traveled to Syria via Turkey to meet with his brother Aden who was fighting there. After his brother's death in June, a cleric approached Mohamud and gave him the mission to attack the U.S.

"Mohamud talked about doing something big in the United States," the federal indictment said. "He wanted to go to a military base in Texas and kill three or four American soldiers execution style."

According to his attorney, Sam Shamansky, Mohamud moved to the U.S. as an infant and had no criminal record aside from a minor theft. His other sibling, a sister, attends college.

The FBI provided much social media evidence showing Mohamud's support for terrorist organizations since at least 2013. He returned to the U.S. in June and was arrested on Feb. 21. He has pled not guilty.

Mohamud is not the only American arrested for plotting against the U.S. The Associated Press reported that 20-year-old John T. Booker of Kansas plotted to attack Fort Riley in the name of the Islamic State.

Also, earlier this year three Brooklyn residents were also arrested with connections to Daesh, also known as the Islamic State.