Updated

Prosecutors will present their case to a federal grand jury Wednesday against a man accused of plotting a suicide bomb attack at an airport in Kansas where he worked as an avionics technician.

FBI investigators said Terry Lee Loewen was attempting to take what he believed was a car bomb onto the tarmac at Mid-Continent Airport in Wichita when they arrested him Friday. Loewen, 58, was charged that day with attempting to use a weapon of mass destruction, attempting to damage property and attempting to provide support to terrorist group al-Qaida.

But federal prosecutors said they would also seek a grand jury indictment. They must show their probable cause evidence either at the secret grand jury proceeding or at a public preliminary hearing tentatively scheduled for Friday. Most federal prosecutions are charged by indictment. An indictment would make the preliminary hearing unnecessary.

The initial criminal complaint outlines an undercover sting in which Loewen and two FBI agents posing as conspirators hatched a plot to place a vehicle full of explosives at the airport. Court documents said he timed the operation to cause "maximum carnage" and death.

In a letter to a relative that prosecutors say Loewen wrote two days before the planned attack, he said he expected to be martyred for Allah by the time the letter was read. He said his only explanation was that he believed in jihad, or holy war, for the sake of Allah and his Muslim brothers and sisters. He acknowledged that most Muslims in the U.S. would condemn him.