One fan held a sign over the tunnel calling for Helton's job, and several other chants and jeers could be heard voicing the same sentiment.
Earlier in the week, Helton indicated he was not concerned about his job security and felt supported by USC athletic director Lynn Swann. But following the loss to one of the worst UCLA teams in recent memory, Helton's tone was somber, and he wasn't nearly as definitive.
Asked if he knows whether he will return next season, Helton said: "That's a great question for Mr. Swann, and out of honor and respect to him, I'll let you ask him that."
Swann was not seen near the USC locker room following the game and did not address the media, which is not outside the norm. Helton said he spoke with Swann in the locker room after the game.
"He just hugged my neck in there and said, 'Coach, I'll see you Monday,'" Helton said, referring to the standing Monday meeting they have.
A loss for the Bruins (3-8, 3-5) would have equaled the most they've ever had in a single season. USC (5-6, 4-5) now needs to beat No. 3 Notre Dame next week in Los Angeles to reach bowl eligibility.
The last time USC failed to win six games was in 2000, which led to coach Paul Hackett's dismissal and the arrival of Pete Carroll.
"Nobody wants to see him go," USC freshman quarterback JT Daniels said of Helton. "Everybody here that knows him, loves him. If you blame Clay Helton for that loss, then you have no idea what football is.
"There are things that players aren't executing, and that's it. The players' part of the ballgame is to make the plays. We have the opportunity."
After winning the Rose Bowl in Helton's first full season as coach in 2016 and winning the Pac-12 last year, the USC fan base quickly lost patience with this year's team, which has lacked discipline and has struggled with inconsistency.
"I know the job," Helton said. "The job is, if you win, people are going to pat you on the back, and if you lose, they're going to get after it. And if you don't like it, don't be in this profession. It rolls off my back. I'm not worried about it."
Helton fired offensive line coach Neil Callaway and took over playcalling duties from offensive coordinator Tee Martin two days after the Trojans lost to Arizona State on Oct. 27.
USC DL throws a punch, hit with unsportsmanlike conduct penalty
After a play, Brandon Pili hits a UCLA offensive lineman and is reprimanded on the sidelines in the second quarter.