The gunman, armed with a shotgun and two handguns, opened fire Thursday in a lecture auditorium, shooting and killing six students and injuring 15 others before killing himself.

Just two years ago, Northern Illinois University honored the man with a dean's award for his sociology work, the Chicago Tribune reported. He had established himself as an authority on prison systems, having co-authored a manuscript on self-injury in prison and the role of religion in the formation of early prisons in the United States.

Two law enforcement sources identified the gunman, who was an Northern Illinois University student in spring 2007, was a graduate student at the University of Illinois at Urbana-Champaign. The Tribune didn't name the shooter because police haven't completed the identification of his body.