A Virginia Tech doctoral student lunged at a fellow student in a campus cafe and began cutting her head off with a knife while staring at her face with a blank, determined expression, a cafe worker testified Friday.

Corey Cox said he had just returned from a break at his job at Au Bon Pan in Tech's Graduate Life Center on Jan. 21 when he heard growling and screaming. He looked up to see Haiyan Zhu attacking Xin Yang.

Click here for photos of the crime scene.

"He was already going at her, cutting her head off," Cox testified at a preliminary hearing for Zhu.

Cox said he dove behind the counter and called 911 while customers and his manager ran from the coffee shop. At least twice during the call, Cox said, the dispatcher asked him to look around the shop so he could give her more information.

Each time he looked up, Cox said, Zhu was on top of Yang, who was on the floor. Zhu stared at Yang's face as he cut through her neck, Cox said.

"It wasn't really an angry face at all," Cox said. "It was just a really blank, determined look."

By the time police arrived, Zhu was holding the woman's head in his hand, an officer testified.

"I saw a body lying and I saw a gentleman walking toward me with a head in his hand," testified Nicole Irvine of the Virginia Tech Police Department.

Irvine said he dropped the head when she ordered him to put his hands in the air.

After hearing from the two witnesses, Montgomery County General District Judge Gino Williams certified first-degree murder charges against Zhu, 25. The next step is a grand jury indictment before a trial can be scheduled.

Zhu was studying for a doctorate in Tech's agriculture and applied economics program. Yang, 22, had just arrived at the school two weeks before to study for a master's degree in accounting. She listed Zhu as her emergency contact. The extent of their relationship is not clear, but both students were from China. After his arrest, Zhu talked about Yang in the present tense and said she was not his girlfriend yet, Irvine testified.

Witnesses have told police that Zhu and Yang were drinking coffee together and had not been arguing before the attack.

Irvine said she found a kitchen knife lying on a table in the cafe and Zhu told her he had knives and a hammer in his backpack.

Zhu's lawyer did not present any witnesses, which is common at preliminary hearings. Zhu's lawyer also made no comment afterward.

Zhu showed no emotion as he sat manacled and shackled, often looking down and writing during the hearing. Four bailiffs stood behind him. An interpreter sat beside Zhu, whispering a translation of the proceedings.

Zhu, who is being held at a local jail, was evaluated at a state mental hospital and found competent to stand trial.