DALLAS , Texas ( CNN ) -- A terrorism suspect accused of plotting the bombing of a skyscraper made his first appearance in federal court Friday . Hosam Maher Husein Smadi said through his lawyer that he understood the charges Friday . Hosam Maher Husein Smadi , a 19-year-old Jordanian , said little during a 20-minute hearing at the Dallas federal courthouse . His lawyer , however , said Smadi understood the gravity of the charge . Judge Irma Ramirez set a probable cause hearing for October 5 . Smadi initially drew authorities ' scrutiny because of his violent posts on an extremist chat site , court papers indicate . He was arrested Thursday in a sting operation , the FBI said . Federal officials said Smadi , who entered the United States illegally and lived in Texas , tried to set off an explosive attached to a vehicle at the base of the 60-story Fountain Place office tower . Long before authorities arrested Smadi , however , they were following his Internet discussions , according to a court affidavit . `` Smadi was discovered by the FBI within an online group of extremists , '' the affidavit says . `` Among many others in the group who espoused and endorsed violence , Smadi stood out based on his vehement intention to actually conduct terror attacks in the United States . '' Undercover officers then contacted Smadi , posing as members of an al Qaeda sleeper cell . After months of conversations , the agents considered Smadi a legitimate threat . Smadi picked several targets to attack , including the Dallas-Forth Worth airport , before deciding on the skyscraper , which houses Wells Fargo Bank , the affidavit says . It details a conversation that Smadi is said to have had with authorities : . `` I have decided to change the target , '' he said , according to the affidavit . `` God willing , the strike will be certain and strong . It will shake the currently weak economy in the state and the American nation , because this bank is one of the largest banks in the city . '' Smadi said many times that he wanted to commit violent jihad and he was a soldier of Osama bin Laden , the affidavit says . Undercover agents tried to get Smadi to `` re-evaluate his interpretation of jihad , '' saying there were nonviolent ways to commit the act . But `` Smadi again communicated his continuing commitment for violent jihad , '' the affidavit says . After casing the bank in July , Smadi told an undercover agent he would target it , according to authorities . Initially , Smadi told the agent he wanted to bomb the bank on September 11 but decided to wait until the Islamic holy month of Ramadan ended on September 20 , authorities said . After receiving what he thought was an explosive from an undercover agent , Smadi drove a car with the fake bomb into a parking garage under the skyscraper , authorities said . Watch how a Jordanian was given fake explosive » . Smadi thought he could detonate the bomb by dialing his cell phone , they said . When he dialed , the number rang a phone in authorities ' possession , the affidavit says . Counterterrorism officials arrested Smadi on Thursday before publicly disclosing a similar but unrelated terrorism sting arrest Wednesday in Springfield , Illinois . A federal law enforcement official familiar with the cases said authorities feared that word of the Illinois arrest could tip off the Texas suspect to the sting operation . Watch what the recent terror arrests mean » . A charge of attempting to use a weapon of mass destruction carries a potential sentence of life in prison and a $ 250,000 fine . In the Illinois case , undercover FBI agents foiled a plot to bomb Springfield 's federal building , authorities said . In neither case did authorities find ties to known terrorist groups . Journalist Todd Bensman and CNN 's Jeanne Meserve , Sean Callebs and Terry Frieden contributed to this report .
NEW : Suspect initially wanted to stage attack on September 11 , authorities say . Affidavit : Teen accused in Texas bomb plot wrote violent posts on extremist Web site . Hosam Maher Husein Smadi accused of plotting to bomb Dallas skyscraper . Smadi told plans to undercover FBI agents , authorities say .