Updated

A self-professed jihadist who threatened online to commit a "Fort Hood-inspired" act of terror was weeks away from reporting for basic training when the military learned of his radicalism - which had apparently been on display for months in online posts where he praised Usama bin Laden and pledged to die for radical Islam.

The man identified in an FBI-sourced alert as "Booker, also known as Muhammad Abdullah Hassan" appears to be the same person who wrote of his jihadist aspirations, cheered on the murder of American troops in Iraq and praised the Al Qaeda terror boss in posts stretching back months, FoxNews.com has learned.

“Getting ready to be killed in jihad is a HUGE adrenaline rush! I am so nervous," read a March 19 post on the Facebook page authorities believe belonged to the subject of the alert. "NOT because I’m scared to die but I am EAGER to meet my lord.”

John Thomas Booker, 19, of Topeka, Kan. enlisted in the Army in February and
was due to report for basic training on April 7. But the FBI interviewed him in March and alerted the Army, which formally discharged him last week. He is now in an undisclosed mental health facility, sources told FoxNews.com.

"The Army was notified on 21 March by federal law enforcement of Mr. Booker's jihad sympathies and worked jointly to prevent a potential threat," Army spokesman George Wright told Fox News. "Mr. John Booker enlisted on Feb. 7, but never attended basic training. He was released from the delayed entry program on March 24. Mr. Booker never expressed any anti-American sentiment during the recruiting process."

But even after his discharge, on March 28, an alert based on information provided by the FBI and sent to law enforcement and military agencies warned of "Planned Ft. Hood-inspired Jihad against US Soldiers by Army Recruit."

“On 20 March 2014, the Kansas City Division FBI became aware of an individual named BOOKER aka Muhammad Abdullah Hassan who had publicly stated his intention to commit jihad, bidding farewell to his friends and making comments indicating his jihad was imminent,” the alert read. “BOOKER had been recruited by the US Army in Kansas City, MO in February 2014 and was scheduled to report for Basic Training on 7 April 2014. Kansas City Division Agents interviewed BOOKER on 20 March 2014.”

The alert, which was sourced to “an FBI agent,” stated it was distributed to “inform and protect officers who may encounter this individual or others exhibiting the same aspirations.”

Four days later, on Tuesday, the FBI downplayed the "routine" alert, saying it was not actively searching for Booker. The agency said it did not believe he posed an "imminent threat," despite the original alert's invocation of the Fort Hood shooting, where an Army psychologist killed 13 and wounded more than 30 on a Texas military base in 2009.

“We have interviewed this individual,” an FBI spokesman said. “There is not a manhunt and there never was one. There is no imminent threat to public safety, nor should the public be concerned that this threat exists from an individual at large."

But weeks earlier, even as Booker was being recruited by the Army and preparing to report, a check of his activity on various social media sites might have revealed he was not fit to serve. As far back as five months before enlisting, he was actively posting in support of the murder of U.S. troops overseas.

The Facebook profile believed to have been created by Booker was taken down on Monday night, though FoxNews.com obtained numerous screen shots of his posts and photos. The page, as well as numerous YouTube rants, painted a picture of a troubled radical with bad intentions long before he was recruited by the Army, or interviewed by the FBI's Kansas City office.

“I wanna be a martyr (shaheed)!!! YA, brothers and sisters," he said on a YouTube video some seven months ago. "Make a dua for me asking Allah to make me a martyr, PLEASE!!!!!!!!!! My name is above in blue.”

Around the same time, he commented on a video called “American soldiers A day in iraq Part 1,” saying, “I'm am Muslim. Muslims had no business in Iraq.” The video shows, graphically, American troops under fire in Iraq in 2008.

Booker, who attended Topeka West High School, where he was a member of the Junior ROTC program before graduating in 2012, at some point began calling himself Muhammad Abdullah Hassan. According to his now-defunct Facebook profile, Hassan “Studied Protection, Security and Investigation at Flint Hills Job Corps” and lives in Topeka.

On March 9, a month after he enlisted at the Kansas City recruiting station, Booker posted a series of photos of Usama bin Laden holding various weapons. “Allahu Akbar J Sheikh Osama bin Laden and his army..” reads a post by the photo.

On March 15, a post on the Facebook page expressed Booker's desire to die for his beliefs.

“Oh those of the ummah of the Prophet Muhammad(S)j. I will soon be leaving you forever so goodbye!" it read. "I am going to wage jihad and hopes that i die. I want to be with my lord so bad that I cry but I will miss you guys I am not going to lie. I wish I could give you guys more but I am just a guy who is so very poor. I am telling you I am so broke that my pockets are soreJ I cannot wait to go to the Prophet Muhammad’s(S) door and prank Isa bin Maryan and party so hard that it will rock Jannah to its core. Only Allah knows what the future has in store so that should make you fear Allah much much more.”