A graduate student from Saudi Arabia has admitted fatally stabbing a professor at upstate Binghamton University.

Abdulsalam al-Zahrani, 48, pleaded guilty to first-degree manslaughter yesterday, three months after he was sent to a psychiatric center where experts determined he was schizophrenic but mentally competent to stand trial on a murder charge.

Broome County DA Gerald Mollen says al-Zahrani had come to believe Richard Antoun was part of a plot against him and attacked the 77-year-old professor in his office on the suburban Vestal campus in 2009.