ORLANDO, Florida (CNN)  -- The man accused of trying to sneak bomb-making materials on a flight from Orlando to Jamaica admitted he planned to build a bomb after he landed, according to an FBI agent.



Witnesses say the man arrested Tuesday was "rocking left and right and up and down."



The man said he planned to "detonate the device on a tree stump in Jamaica, but later told us he was going to show friends how to build explosive devices like the kind he saw in Iraq," FBI agent Kelly Boaz said in a court affidavit.



The first court appearance for the man, Kevin Brown, was postponed Wednesday to allow government officials time to look into whether he suffers from mental illness.



U.S. Army officials said Brown was in the service from September 1999 through December 2003, when he received an honorable discharge. Although his record did not show a deployment to Iraq, he received an Army commendation medal in 2003 for serving in support of Operation Iraqi Freedom, officials said.



His court-appointed attorney declined to comment.



Brown, a Jamaican national, was arrested Tuesday on charges of "carrying a weapon or explosive on an aircraft," the FBI said.



He was taken into custody after an air safety officer noticed him acting strangely as he waited to board an Air Jamaica flight, federal authorities said.



He appeared in court Wednesday but government officials asked for the delay, saying there were indications Brown might have a history of mental illness.



A new hearing is scheduled for 3:30 p.m. Thursday.



Transportation Safety Administration officials said a "behavior identification officer" noticed Brown acting strangely around noon Tuesday as he approached a ticket counter.



Officials said Brown, who is believed to be in his early 30s, had checked baggage that contained two galvanized pipes, end caps, two containers of BBs, batteries, glass bottles containing nitromethane, a laptop, bomb-making literature and one model rocket igniter.



Boaz, a member of law enforcement bomb squad, said the items could have been used to make bomb.



"The items found in Brown's baggage constitute an incendiary device," Boaz said in court papers. "The nitromethane was in a breakable container and the model rocket igniter would act as the wick."



Initial record checks indicate Brown was in the United States legally, the FBI said. According to the bureau, he was living on the streets in Orlando, "sleeping in the open." Federal investigators said he seems to have been living in several places, sometimes with relatives, and they don't know his home town.



"It appears to be an isolated incident, but our investigation is continuing," the FBI's David Couvertier told CNN. As part of the probe, officials are looking at whether Brown has ties to any organized group, he said. The FBI is being aided by Orlando police.



Airport officials said several ticket counters were temporarily closed during the incident, and 11 flights were delayed. Airport spokeswoman Carolyn Fennell said Air Jamaica, Air Canada, West Jet and Frontier flights were among those delayed. E-mail to a friend



CNN National Correspondent Susan Candiotti and Rich Phillips contributed to this report.
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