Authorities say four people were shot and wounded during a Halloween party on the University of Southern California campus and two suspects were in custody.

It happened around 11:45 p.m. Wednesday outside the Ronald Tutor Campus Center, where 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.

That victim was critically wounded. Three bystanders were taken to the hospital with less serious injuries.

The party appeared to be packed with students dressed for the occasion. One student told The Los Angeles Times that he saw a man shot in the leg asking for someone to give him a ride, apparently to a hospital.

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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.

An official at the school told the paper that campus security were monitoring the party and were able to respond swiftly to the incident and apprehend the suspects.

Click for more from The Los Angeles Times. 

The Associated Press contributed to this report.