Two people have been killed and four others wounded, three critically, in a shooting at the University of North Carolina in Charlotte.
Police say one suspect, who some local media reported was a male student at the school, was taken into custody following the rampage on the last day of classes for the academic year.
Final exams were scheduled for next week.
Charlotte-Mecklenburg Police Department spokeswoman Sandy D'Elosua said the individual arrested was believed to have acted alone.
Television station WBTV in Charlotte reported gunfire erupting about 5.45 pm local time near the university's Kennedy Hall administrative building and one person arrested.
"We are in shock to learn of an active shooter situation on the campus of UNC Charlotte. My thoughts are with the families of those who lost their lives, those injured, the entire UNCC community and the courageous first responders who sprang into action to help others," Charlotte Mayor Vi Lyles said on Twitter.
Susan Harden, a professor on campus since 2011 who also serves on the Mecklenburg County Board of Commissioners, expressed disbelief.
"This is a day at the end of the semester, when students are doing performances, presentations ... this is just the worst thing," she said at the police staging area.
"Our campus is so safe. So safe. I've never felt unsafe on our campus. I'm heartbroken."
Mecklenburg Emergency Management Services, an independent agency that handles emergency services for the county, confirmed on Twitter two people were dead on scene and four others were taken to a hospital, two with life-threatening injuries.
WSOC-TV reported the shooter was a student at the university.
The suspect was not immediately identified by police, who set up a media staging area near the school.
"Run, Hide, Fight. Secure yourself immediately," the university said on Twitter shortly before 6 pm.
The school said later on its website the campus was on lockdown and that students and staff should "remain in a safe location".
Video footage aired on local television and posted to social media showed scenes - increasingly familiar with the rise of school gun violence in the United States - of students evacuating campus buildings with their hands raised as police officers ran past them toward the scene of the shooting.
According to its website, the University of North Carolina at Charlotte enrols more than 26,500 students and employees 3000 faculty and staff.