Suspected gunman Steven Jones, a freshman at Northern Arizona University in Flagstaff is shown in this booking photo released on October 9, 2015. [Photo/Agencies]

A university spokeswoman said the Arizona incident occurred in a parking lot next to a residence hall for Greek organizations - fraternities and sororities - around 1:20 a.m.

"We don't know the facts yet about what brought them together, or what caused the confrontation," Fowler said.

Delta Chi International Fraternity executive director Justin Sherman said the four victims were members of the fraternity but the alleged gunman was not.

Jones, who did not try to flee, was arrested by university police and is cooperating with authorities, Fowler said. He said guns are not allowed to be carried on campus.

The university said Jones was charged with first-degree murder and three counts of aggravated assault, and that he would be arraigned by video on Friday afternoon.