An 18-year-old Northern Arizona University freshman, Steven Jones, was taken into custody by police over allegations he shot and killed one and wounded three others in a campus parking lot incident about 1:20 a.m. Friday.
North Arizona University Police Chief G.T. Fowler said at a Friday morning press conference on national television the shooting stemmed from a confrontation between two groups of students, but did not elaborate.
He also said the suspect, Jones, "did not run from the scene" when police approached, and was taken into custody without incident.
"The suspect is cooperating with police," Fowler said.
The incident occurred on the Flagstaff campus in a parking lot by Mountainview Hall dormitory.
The victims were all students who had been shot multiple times, Fowler said. The three injured students were transported to Flagstaff Medical Center for treatment.
The killed student was identified as Colin Brough, CNN reported, citing the NAU website. The three students who were injured were Nicholas Prato, Kyle Zientek and Nicholas Piring, the university reported.
NAU president Rita Cheng, meanwhile, called this incident a "terrible tragedy."
But the motive is still unclear. Delta Chi fraternity officials at the university said some of their members were involved in the incident but clarified the shooting was not "chapter related," CNN said,
Fowler said more information would be forthcoming as soon as  possible.
"We can't release a lot of additional details," Fowler said at the Friday press conference. "All the resources of [various law enforcement] are assisting us with this investigation. A great many people are involved and need to be interviews."
The university, meanwhile, has put out some information via its Twitter feed.
Early Friday morning, campus officials tweeted:Â "Reported shooting at NAU Flagstaff campus. Shooter in custody. Mountain View Hall residents stay indoors. More details to follow."
Shortly after, the campus sent out another tweet: "@NAUALert Details confirmed 4 victims, 1 fatality, 3 wounded. Shooter is in custody. Situation is stabilized. Campus not on lockdown."
About 25,000 students attend the university, which officials confirmed as a gun-free zone.
Sen. John McCain, who represents Arizona, put out a statement shortly after the shooting that read: "My thoughts and prayers are with families of the person who was killed and the three others who were wounded in the horrific shooting on the campus of Northern Arizona University in Flagstaff early this morning. I appreciate the efforts of all state and local law enforcement officials, first-responders and school administrators, and continue to pray for the recovery of the injured, as well as all those in the NAU community who have been impacted by this terrible tragedy."