A former Lehigh University college student accused earlier this year of leaving racist graffiti for his roommate in their dorm room is now facing charges he tried to poison him.

Yukai Yang, 22, an international student from China, turned himself in on Thursday and was charged with attempted homicide, aggravated assault, simple assault and reckless endangerment, Northampton County District Attorney John Morganelli said Thursday.

The chemistry major allegedly sickened his roommate, Juwan Royal, 22, over a few months with small amounts of thallium and possibly other chemicals, Morganelli said at a press conference. Thallium is a toxic metal that is colorless, odorless and tasteless and can be fatal if consumed.

Yukai Yang is charged with trying to poison his roommate to death and vandalizing the victim's possessions with racist graffiti. Northampton County Department of Corrections

“Initially, Mr. Royal was as dumbfounded by this as everyone else, because he believed they had a fairly cordial relationship as roommates,” Assistant District Attorney Abe Kassis said.

Royal told police at the Bethlehem, Pennsylvania, campus that in February he drank from a water bottle in his room and felt burning in his mouth.

Yang allegedly mixed the chemicals into his roommate’s food, drinks and mouthwash.

Royal became ill multiple times in March and his symptoms, which included dizziness, shaking and vomiting, became progressively worse, Morganelli said. Royal's blood tested positive for the chemical and he was treated for thallium poisoning.

Yang was confronted about Royal's sickness in a follow-up interview in May, a month after he was separately charged with ethnic intimidation, institutional vandalism and criminal mischief for allegedly scrawling a racial epithet on a desk in their room, authorities said.

He admitted purchasing various chemicals with the intent of harming himself if he did poorly on exams and told police he mixed them in foods and drinks stored in their shared refrigerator, prosecutors said.

“The Lehigh University Police Department has worked closely with the District Attorney's Office on the investigation and will continue to do so,” a spokeswoman for the school told NBC News, noting Yang is no longer enrolled as a student. “From the outset, our concern has been the health and safety of the victim of these alleged behaviors and, as such, Lehigh staff and faculty have been providing support, services and assistance.”