Authorities investigate the scene outside a student dormitory in Flagstaff, Ariz., Oct 9, 2015, after an early morning fight between two groups of college students escalated into gunfire leaving one person dead and three others wounded, authorities said. The shooting occurred near the Northern Arizona University campus. [Photo/IC]

Classes were to continue as scheduled on Friday for the school's 20,000 students, university president Rita Cheng told a news conference, calling the incident isolated.

Arizona Governor Doug Ducey and Arizona US Senator John McCain, both Republicans, extended thoughts and prayers to the victims and their families.

Obama reacted to the killings in Oregon by vowing to step up efforts to curb US gun violence. Gun rights advocates said the Oregon shootings underscored the importance of the right of Americans to bear arms and defend themselves.

Just hours after the Arizona shooting, police said one person was killed and another wounded in a shooting at an apartment complex near the campus of Texas Southern University in Houston, and a suspect had been taken into custody.