Washington(CNN) A former soldier who prosecutors say claimed he enlisted to become better at killing Black people was kicked out of the Army following an FBI investigation that uncovered ties to White supremacist organizations and Nazi ideology.

Killian M. Ryan was arrested August 26 and charged with one count of knowingly making a false statement on his application for a secret security clearance, according to court records. On the same day, he was discharged from the Army for "serious misconduct," said Lt. Col. Terence Kelley, an Army spokesman.

Prosecutors say Ryan operated social media accounts where he was in contact with extremists, including where he made the shocking claim about why he decided to join the military.

Ryan had been serving as a Fire Support Specialist and held the rank of Specialist when he was discharged, Kelley said. A Fire Support Specialist gathers intelligence and enemy target positions to help the Army in deploying and firing artillery. The job requires a secret security clearance. Ryan had served with the 2nd Battalion, 319th Airborne Field Artillery and the 1st Battalion, 325th Airborne Infantry Regiment. He had not deployed.

The former paratrooper was discharged for multiple driving under the influence of alcohol violations, according to a defense official, but prosecutors say they found far more serious issues during their investigation.

On his application for a secret security clearance in May 2020, Ryan allegedly said that it had been more than 10 years since he'd been in contact with his father, who has felony convictions for drug violations and auto theft.

But investigators found a number of social media accounts, all allegedly registered to Ryan, which were used to contact his father during the 10-year period. They also found recent photos of Ryan with his father, court records say.

When investigators further probed the accounts, they noted that one of Ryan's accounts had "been in contact with numerous accounts associated with racially motivated extremism," court records said. The account username referenced Sigurd -- a figure in Norse mythology that is sometimes co-opted by White supremacists -- and an email registered to the account referenced Nazi ideology.

On another account, Ryan allegedly posted: "I serve for combat experience so I'm more proficient in killing n*****s." Investigators found that Ryan registered some of these social media accounts with an email that included "naziace1488."

CNN has reached out to Ryan's attorney for comment.

Defense Secretary Lloyd Austin made rooting out extremism in the military one of his top priorities. Though the Pentagon insisted that extremism in the military was only a tiny fraction of service members, officials acknowledged that the January 6, 2021, Capitol riot was a "wake-up call" for the Defense Department.

At least 95 people charged in connection with the January 6 insurrection served in the US military, according to a CNN review of Pentagon and Justice Department records.

Shortly after taking office, Austin ordered a staggered pause in operations throughout the force, known in the military as a stand down, in order to reinforce leaders' expectations of behavior for service members and review the Defense Department policy on extremism.

Late last year, the Pentagon then issued a sharper, clearer definition of extremist behavior that, for the first time, included guidance on social media platforms and posts.