Four people have been shot and wounded during a Halloween party on the University of Southern California campus.
Two people were detained following the shooting shortly before midnight, said an official.
The four victims were rushed to hospitals after the shooting at Tutor Campus Centre.
USC Department of Public Safety Capt David Carlisle says an argument between two men not tied to the school led to one of them pulling out a gun and shooting another person. That victim was critically wounded. Three bystanders were taken to the hospital with less serious injuries.
The violence occurred outside the party attended by about 100 people. Police then declared the campus "shut down" and issued an alert urging students to remain indoors.
USC sent a text alert telling students to stay inside. Hours later, another text said the threat was over and classes would go on as scheduled.
Campus police did not provide any details on the two people who were detained.
www.usc.edu (University of Southern California)