DEKALB, Illinois (CNN) -- Northern Illinois University on Friday identified the man who fatally shot five people in a classroom as Steven P. Kazmierczak, whom police described as an award-winning student "revered" by colleagues and faculty.
Kazmierczak, 27, who police said shot 21 people before shooting and killing himself, was an award-winning sociology student and a leader of a campus criminal justice group, according to school Web sites.
Concealing a shotgun in a guitar case, and tucking three other guns under his coat, Kazmierczak walked into a geology class in an NIU lecture hall Thursday afternoon and began firing, police said. The graduate student stopped to reload his shotgun before he took his own life, police said.
Kazmierczak was a student about 175 miles away at the University of Illinois at Urbana-Champaign, police said, and there "were no red flags" warning of any violent behavior.
One of Kazmierczak's advisers said that she enjoyed having him as a student and that he was "a nice person; he was a nice kid."
"I found Steven to be a very committed student, extremely respectful of me as an instructor and adviser," said Jan Carter-Black, an assistant professor in the University of Illinois at Urbana-Champaign's School of Social Work. Watch Carter-Black deal with painful news »
Carter-Black was assigned to be Kazmierczak's faculty adviser when he enrolled in the school in the summer of 2007, and he was a student in her human behavior and social environment class last fall, she said.
Carter-Black and Chris Larrison -- another School of Social Work associate professor who knew Kazmierczak -- described the gunman as pleasant, considerate and flexible.
"I was so surprised to see this today," Larrison said. Kazmierczak worked on a research project concerning mental health clinics under him, he said.
"It doesn't fit with the Steven" he knew, Larrison said.
The 27-year-old participated fully in the class -- which met for three hours once a week -- until he formally withdrew from it sometime before late September and became a part-time student, Carter-Black said.
He was lightening his course load so he could take on a position in the prison system, she said.
She didn't know if the position was in the federal or state system, but said he had discussed the decision with several faculty members. He later left the position at the prison, she said, but she didn't know under what circumstances.
"He was very committed to pursuing a career with prisoners," Larrison said. He said it was likely that the career interest corresponded with Kazmierczak's concentration in mental health.
Carter-Black and Larrison said Kazmierczak resumed full-time status this semester.
In 2006, Kazmierczak was a student at Northern Illinois, police said, where he worked on a graduate paper that described his interest in "corrections, political violence, and peace and social justice."
The paper said Kazmierczak was "co-authoring a manuscript on the role of religion in the formation of early prisons in the United States."
University police Chief Donald Grady said Kazmierczak "was an awarded student. He was someone that was revered by the faculty and staff and students alike."
Fellow students and faculty described Kazmierczak as "a fairly normal, unstressed person," Grady said. Watch student reaction to shooting aftermath »
People close to Kazmierczak said he was taking medication but had recently stopped, "and he had become somewhat erratic in the last couple of weeks," Grady said.
Police have found no notes that would explain the attack, and authorities have no known motive in the case, Grady said.
Kazmierczak's former landlord, Jim Gordon, said Kazmierczak moved out of DeKalb in June 2007 and left a forwarding address in Champaign.
Gordon said he didn't recognize the picture of his yearlong former tenant "at all," but his records indicated that Kazmierczak "always paid on time, never a noise problem, left the place spotless."
The university sociology department's Web site said he was the recipient of a dean's award for his graduate work in sociology in 2006. He had been accepted for the graduate program that fall, the Web site said.
Kazmierczak also was vice president of the university's Academic Criminal Justice Association, according to the group's Web site, and worked on a paper on self-injury in prisons with the group's current president.
Kazmierczak's paper, titled "Self Injury in Correctional Settings: 'Pathology' of Prisons or Prisoners?" was published in 2006, according to the university's sociology Web site.
The Academic Criminal Justice Association provides "NIU students and members of the DeKalb community with an opportunity to learn about and promote knowledge and understanding of all areas of the criminal justice system, especially corrections and juvenile justice," the Web site says. See photos of the victims and shooting aftermath »
DeKalb police asked the Polk County, Florida, Sheriff's Department to make "next of kin" death notification to Kazmierczak's father, Robert Kazmierczak, sheriff's spokeswoman Carrie Rodgers said Friday.
"Please leave me alone. I have no statement to make," Robert Kazmierczak told CNN affiliate WESH from the porch of his Lakeland, Florida, home.
"It's a very hard time. I'm a diabetic," he said before breaking down in tears. Watch the father react to the media »
School President John Peters said Friday, without giving a name, that the shooter had graduated in 2006 with an undergraduate degree in sociology and then went on to do some graduate work through 2007.
He "had a very good academic record" and "was a very good student," Peters said, adding that there was "no indication" of any trouble involving him.
Kazmierczak had no arrest record and no known history of mental illness, and he had a valid state-required firearm ID card, so he had no problem buying the guns, one law enforcement source said.
Police said the only record of him in DeKalb County Circuit Court was a speeding ticket issued in December 2006. A police officer cited him amid snowy conditions for "failure to reduce speed -- resulting in an -- accident," in a white 2001 Honda. Kazmierczak was 6-foot-4 and 165 pounds, according to the record.
Kazmierczak pleaded guilty and paid a $75 fine. No one was injured in the accident, the record showed. E-mail to a friend