A graduate student from India whose bomb and anthrax threats shutdown the University of Missouri-Rolla was charged Wednesday with making terrorist threats and assaulting a law enforcement officer, authorities said.

Sujithkumar Venkatramolla, 22, was arrested on campus early Tuesday after walking into a civil engineering building armed with a knife, holding paper bag and saying he had a bomb and anthrax, according to authorities.

Police eventually subdued him with a stun gun after he refused to drop the knife, interim Police Chief Mark Kearse said.

Kearse said the student was depressed and apparently distraught over grades.

The bomb and anthrax threats were determined to be phony. Extensive searches of the campus building Tuesday found no trace of explosives, and preliminary tests showed that a white, powdery substance found on the man was nothing more than powdered sugar, said Lt. Col. David Boyle of the Missouri National Guard at Fort Leonard Wood.

"Thankfully, this is a false alarm," university Chancellor John F. Carney III said.

Venkatramolla was charged Wednesday with armed criminal action, resisting arrest, false report of a bomb threat, making terrorist threats, and first-degree assault of a law enforcement officer, said Phelps County prosecutor Courtney George.

Venkatramolla, a civil engineering student, is from Nazambad, India, university spokeswoman Mary Helen Stoltz said. She was not aware of any previous disciplinary issues.

The 5,850-student technological research and engineering campus was shut down for the day by the scare. Twenty-three people, including eight students and a faculty member, were quarantined for several hours but showed no signs of illness and were allowed to go home Tuesday afternoon.

Stoltz said classes at the south-central Missouri university resumed Wednesday.

The arrested student lived in an off-campus apartment and authorities interviewed his roommate, Mayor Bill Jenks said. Jenks would not provide details but said no one else would be charged.