Police say four people were shot and wounded during a Halloween party on the USC campus shortly before midnight Wednesday. Two people have been detained.
The shooting happened at the Tutor Campus Center. The victims were rushed to hospitals. Their conditions were not immediately known.
About 100 people had gathered for a party hosted by a student organization.
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.
One man was shot several times and critically wounded. Three bystanders were taken to the hospital with less serious injuries.
The Los Angeles Times reports 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.
Carlisle says the suspects were arrested about 10 minutes after the shooting and the alert was called off.
In April, two USC graduate students from China were shot to death in a car near the campus.