A gunman who shot and killed a professor on the campus of Delta State University in Mississippi is still at large.
The victim has been identified as Ethan Schmidt, who worked in the history department at the Cleveland campus.
Police are searching for the gunman who is still at large but reportedly now off campus.
Shortly before 11am local time (3am NZT), all campus buildings were locked from the inside and officials advised people to shelter.
Police were clearing students from buildings on campus.
Campus remains under lockdown. Please do not leave the building. Stay away from windows. More information will be sent out as available.— Delta State (@DeltaState) September 14, 2015
Schmidt, who specialised in Native American and colonial history, was shot in his office inside the university's Jobe Hall building, police said.
Don Allan Mitchell, a colleague, called Schmidt "a gentleman in every sense of the word" and "a terrific family man".
Roughly 3,500 students are enrolled at the university near the Arkansas border.
Classes have been cancelled for the day.
Freshman Noah Joyner, 18, said he stayed inside a bathroom in his dorm buildings during the lockdown.
"There were people banging on the doors to have somebody let them in," Mr Joyner, a swimmer at Delta State, told the Associated Press. "It was pretty terrifying to hear people banging on the door."
Police helicopters are circling campus and hundreds of officers have swept buildings.