When a gunman opened fire at the Borderline Bar & Grill in Thousand Oaks, Calif., on Wednesday night, Sgt. Ron Helus rushed in.

He would not make it out. Sergeant Helus was killed in the shooting at the crowded country music bar, one of 12 people who lost their lives in the attack.

[Read here for the latest developments on the Thousand Oaks shooting.]

His colleagues in the Ventura County Sheriff’s Department said that toll might have been even higher if not for Sergeant Helus.

“He went in to save lives, to save other people.” Sheriff Geoff Dean said Thursday, adding that Sergeant Helus was set to retire this year. Sheriff Dean said that Sergeant Helus had a conversation with his wife on the phone before entering the bar.

“He was a true cop’s cop,” Sgt. Eric Buschow told CNN of his colleague. Sergeant Buschow said he joined the force about the same as Sergeant Helus 29 years ago. Over the years, Sergeant Helus worked in various departments within the agency, including narcotics and SWAT.

Sgt. Ron Helus

“He had a natural instinct going after crooks,” Sergeant Buschow said. “He did it with enthusiasm and a great deal of intelligence.”

Sergeant Helus loved the outdoors and enjoyed fishing with his son in Sierra Nevada. On his LinkedIn page, he said that in addition to his policing job, he owned a firearms safety training business called Gun Control.

“I don’t think there is anything more heroic than what he did,” Sergeant Buschow said. “He went in there to save lives.”

Gov. Jerry Brown expresses condolences for ”the Thousand Oaks community and those who lost friends and loved ones.”

“We are grateful for law enforcement and others, including Ventura County Sheriff’s Sgt. Ron Helus, who took heroic action to save lives last night,” Mr. Brown said.

The Ventura County Sheriff’s Department planned a 10 a.m. procession to accompany Sgt. Helus’ body from the hospital to the county medical examiner’s office.

Sheriff Dean, who announced in January that he would not seek a third term, said that his last day on the force was Friday. “I’m no longer the sheriff by tomorrow at midnight,” said Sheriff Dean, who has been in law enforcement for more than 40 years.