Two men have been charged with first-degree murder for beating Feng Liu, a professor at the University of North Carolina's (UNC) Eshelman School of Pharmacy, to death.

According to the Charlotte Observer, Liu went on a walk after lunch Wednesday, a daily routine, when Derick Davis II, 23, and Troy Arrington Jr., 27, jumped him. The assault was a robbery, but Liu, 59, died early Thursday from a head injury.

Liu's laboratory colleagues said the professor usually took a walk after lunch and would keep a quick pace for about 30 minutes as he cut through campus and surrounding neighborhoods in Chapel Hill.

"I am heartbroken over this horrible tragedy," UNC Chancellor Carol Folt said in a statement. "I want to assure you that safety and security of students, faculty, staff and visitors on Carolina's campus and in the surrounding community is my highest priority."

Lt. Josh Mecimore, a UNC spokesman, said a witness contacted police with information that lead the authorities to the suspects. During a court appearance Thursday, prosecutors said the two men hit Liu in the head with a rock.

"I think the school's in shock, in mourning," Russell Mumper, vice dean of the UNC School of Pharmacy, told WNCN. "The news hit hard. Feng Liu had been a member of our community for a decade. Highly respected colleague, faculty member."

Blake Nelson, a graduate student at UNC, pointed out that the neighborhood in which Liu was attacked was a quiet residential area, home to people like himself, families and faculty members.

"A safe and secure environment is fundamental to our quality of life in Chapel Hill and, as a community, we must not tolerate such senseless violence," Mark Kleinschmidt, the mayor of Chapel Hill, told WNCN. "The Town and the University continue to partner on those matters impacting quality of life in Chapel Hill, public safety being chief among them."