The Los Angeles Police Department confirmed late Thursday afternoon that at least one person was arrested in the shooting, but they did not release the name of the suspect or suspects.
This came as the condition of one of the shooting victims, who had to undergo surgery for his wounds, improved.
According to officials, an argument broke out at a campus-approved gathering at the Ronald Tutor Campus Center. One person opened fire, striking the intended target three or four times in the torso, officials said. That person, identified as former Crenshaw High School football star Geno Hall, was taken to a hospital in critical condtion.
Three innocent bystanders were also shot, but their injuries were said to be non-life threatening. Investigators said two people attempted to flee the scene, but they were detained near Parking Lot 6 on campus. A gun was also found in the area.
"Based on the interviews of the witnesses they have so far, the detectives have developed enough probable cause that they're going to make an arrest this morning. They detained two individuals, and one of those two will be arrested for attempted murder," said Cmdr. Bob Green of the Los Angeles Police Department.
Hall, who was named player of the year in 2009 by a panel of sportswriters, underwent surgery Thursday morning and was said to be in fair condition Thursday afternoon. Several of his friends posted messages on his Twitter page, wishing him well.
Authorities said there were 400 people at the event sponsored by the university's Black Student Assembly, and it was open to the public. The shooting happened outside the gathering, near a long line that included non-USC students. All four victims and the two suspects are not affiliated with the university, officials said.
"I heard four or five consecutive shots, people started screaming and running towards us, " said Astrid Solorzano.
USC was on lockdown for about three hours. Students were notified via text and email to stay inside. The university later sent a message saying the threat was over and that classes would go on as scheduled.
USC officials said they have beefed up security in and around campus in recent months, following the fatal shooting of two graduate students in April. They believe Wednesday's shooting was an isolated incident. Still, some students said they are worried about safety on campus.
"I don't come out at night. I go home before the sun sets. If I come out, I drive my car with my friend in the car. We always go home early," said student Teresa Zang.