Feds: Passenger had murder directions on computer

In addition, Yongda Huang Harris had items on his computer revealing he has a "strong interest" in sexual violence against girls, including a video titled "Schoolgirls in Cement," Assistant U.S. Attorney Melissa Mills said.

One publication was entitled "Man Trapping" and showed how to hunt and trap humans, she said. He also had a document with schedules for schools in Japan showing when students arrived and left.

The prosecutor detailed the discoveries during a court appearance by Harris, 28, a Boston University graduate who had been working in Japan as a junior high school teacher.

The bespectacled Harris was shackled in handcuffs and wore a white prison-issued jumpsuit, along with a blue surgical mask over his mouth due to a throat infection.

Before the detention hearing, he crossed and rubbed his arms, appearing to be cold. He often turned and spoke with his attorney Steven Seiden.

U.S. Magistrate Judge Paul Abrams declared Harris to be a flight risk and ordered him held without bond until he stands trial.

Harris is charged with one count of transporting hazardous materials, for the grenade, and could face up to five years in prison if convicted. He did not enter a plea.

Seiden said the weapons Harris was carrying were meant for protection and necessary because Harris was once attacked on the streets of Boston.

"He may have interests that are not of the norm, but that doesn't mean he's carrying out any type of harm to anyone," said Seiden, who described his client as shy and timid.

Seiden also said Harris didn't have any previous psychological issues.