The 19-year-old man arrested on suspicion of wounding four people at a Halloween party on the USC campus was identified as a security guard.
Brandon Spencer of Inglewood was arrested early Thursday on the campus. A family friend at the apartment complex where he lives told the Los Angeles Times that Spencer was a "good kid."
California Bureau of Security and Investigative Services records reviewed by The Times showed Spencer has a current security guard license.
Authorities initially said two people were detained, but it was unclear who the other person was, or if he was still in custody.
The gunfire broke out at a party sponsored by the Black Student Assembly and attended by about 400 people.
The gunman opened fire on a former Crenshaw High School football star, Geno Hall, who was wounded several times and expected to survive. Three other people, none of them students, suffered wounds authorities called non-life-threatening.
USC President C.L. Max Nikias said school officials were "carefully assessing and reviewing all of the university's policies regarding visitors and events held on campus."
Only students with USC identification, or college students with identification from their schools, are supposed to be admitted to on-campus parties.
The Halloween shooting came in the wake of an April 11 shooting near the campus that left two USC graduate students from China dead. Two suspects have been charged with murder.
The shooting occurred four years after USC sprinter Bryshon Nellum, who won a silver medal at this year's London Olympics, was shot in both legs at a Halloween party just off campus.