There were about 50 people inside the building
One person has been killed and at least another one injured after a gunman opened fire at a university business school in the US city of Cleveland, police said.
Police said the gunman - reported to be in camouflage and armed with a semi-automatic rifle - began firing shortly after 1600 local time (2000 GMT) at the building at the Case Western Reserve University.
Witnesses said the gunman was firing indiscriminately, sending terrified fleeing for their lives.
It is believed up to 50 people may have been inside.
"We're all shaking and quite scared," Tracy Warner told the Associated Press news agency from a third-floor office where she was hiding with several other people.
The standoff ended seven hours later after police stormed the building arresting the alleged gunman.
"We believe he is the shooter or one of the shooters," Police Chief Edward Lohn said without giving any details.
The large building houses the Weatherhead School of Management and has 9,500 students.
It is believed that few students were inside the building when the shooting began as final exams were completed last week.
This is the latest in a string of fatal shootings at American schools.
Last month, a 14-year-old boy killed his headteacher at a school in Pennsylvania, before turning the gun on himself.
In 1999, in one of the worst massacres in US schools, 14 students and a teacher died after two teenagers opened fire at the Columbine High School.