Nick Steinwender, who is part of the university's student government, said his friends were inside the bar when the shooting started.
Civilians and other deputies pulled Sergeant Helus from the bar and he was taken to Los Robles hospital, where he died an hour later.
Authorities confirmed the 29-year-old shooter was dead at the scene.
"Ron was a hardworking, dedicated sheriff's sergeant who was totally committed", Mr Dean said. He gave his all.
Dean, meanwhile, said investigators have only found one weapon at the scene.
Authorities now say there are at least 11 victims in the shooting, including the deputy.
When the gunman entered, people screamed and fled to all corners of the bar, while a few people threw barstools through the windows and helped dozens to escape, witnesses said.
The incident was reported at the Borderline Bar and Grill in the town of Thousand Oaks, a quiet, upscale residential suburb of Los Angeles.
"A gentleman, who walked in through the front door, shot the girl that was right behind the counter", said Holden Harrah, who witnessed the shooting.
"Within a split second, everybody yelled "get down", she said.
Sgt. Ron Helus was one of 12 people killed by a gunman inside a Ventura County nightclub late Wednesday, but to his comrades, he was a family man, a fisherman and an "excellent street cop". Dean said Helus undoubtedly saved lives by going in to confront the gunman.
The venue was holding a weekly "college night" attended by around 100 people.
"It was chaos, people jumping out of windows, people hopping over gates to get out", he told KABC-TV. He said Helus was the first responder and was immediately hit with multiple gunshots.
The shooter, using a short-barreled handgun, was described by witnesses as wearing a black trench coat and eyeglasses, and had a black beard.