Update at 9.30pm: Police has named university employee Shannon Lamb as a ``person of interest'' in the shooting of history professor Ethan Schmidt.
The suspect is no longer believed to be on the campus.
Investigators also say they have information suggesting Lamb may have been involved in another killing in the south Mississippi city of Gautier, about 300 miles away.
Gautier police said that a woman was found dead in her home, and that Lamb is the suspect in her death.
Shannon Lamb (left) is on the run for killing Professor Schimdt (right). Police looking for Shannon Lamb. pic.twitter.com/hsulBaozDL— Ava- I love my USA! (@WEdwarda) September 14, 2015
Update at 7pm:
A professor has been shot dead in his office at a US university and the campus is on lockdown after reports of a gunman on the loose.
The academic died at Delta State University in Mississippi. Officials said he was aged in his mid-50s.
University spokeswoman Jennifer Farish said she was not yet able to identify the man, saying it was still an “active situation.” It is unclear whether anyone else was wounded.
The lockdown began about 10:45 am local time, with the university advising students, faculty and staff to take shelter and stay away from windows.
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
The university’s Twitter account said the shooter was spotted near Jobe Hall.
State and local law enforcement agencies have responded.
The 3,500-student university is in Cleveland, in Mississippi’s Delta region near the Arkansas-Mississippi state line.
Mississippi Department of Public Safety spokesman Warren Strain said a man who is believed to be the shooter was still at large. He said a description was not immediately available.
“Fortunately for us, our public safety officers and university officials have trained many of us for active shooter situations,” Don Allan Mitchell, an English professor, wrote in a Facebook message to The Associated Press.
“Many students are locked-down in classrooms, and professors and staff members are telling them the protocol. Plus, we are all texting and Facebooking each other to make sure we are safe.”
He said police helicopters were in the air, and officers were sweeping buildings.
However, another English professor, Bill Hays, said the university did a poor job of communicating with faculty, staff and students about the emergency situation.
“It’s really frustrating because there is no campus-wide updating from a central command center. Everything we’re getting is just rumours,” Mr Hays said in a phone call from his office in Keithley Hall, across the street from the shooting site.