A veteran Los Angeles County sheriff's deputy accused of having sex with a teenage girl was given the department's highest honor in 2003 for saving a woman's life.

John Augustus Rose II, 43, was arrested Thursday on suspicion of having sex with a minor, who was 14 or 15 years old, between February and June while he was off duty, authorities said Friday.

The department launched an investigation after officials said they were alerted about Rose on Aug. 7 by the San Bernardino County Sheriff's Department.

"As soon as we heard about it, we investigated it," department spokesman Steve Whitmore told The Times.

He said Rose is "well thought of" in the department. "But this is obviously just inexcusable," Whitmore added.

Records show Rose — a 22-year veteran — was awarded the Medal of Valor for the daring rescue he and another deputy made during the Curve fire in the San Gabriel Mountains that burned 21,000 acres.

"They are just like angels," Soldier Creek resident Sigrid Hopson told The Times in 2002.

According to media reports and a description of the event by the Sheriff's Department, Hopson was trapped in her cabin with her dogs, surrounded by fire, when the deputies went in to rescue her.

Fearing she and her dogs would be burned to death, Hopson called her ex-husband and told him she was going to shoot her dogs and then herself to spare them a fiery death. The ex-husband alerted authorities, and Rose and another deputy went to save her.

According to the department, the deputy and Rose "drove seven miles into the burning area, over burning brush and trees, through recent rock slides, and over boiling mud and ash-soaked streams" to get to Hopson.

They got as far as they could, then Rose ran the next quarter-mile on foot.

When he got to Hopson's cabin, Rose found her sitting in the middle of the floor, a gun to her head and her dogs either dead or missing. He persuaded her to leave and ran with her back to the vehicle.

"My partner told her to close her eyes and put her seat belt on, because she didn't want to see what was in front of us," Rose said.

They made it out while the vehicle's undercarriage was on fire and two tires were blown out.

Most recently, Rose was assigned to the Community Oriented Policing Services Bureau, which aims to help residents by taking a "holistic approach to problem-oriented policing," according to the department.

Rose was relieved of duty Thursday without pay. He was being held in lieu of $325,000 bail.

Whitmore said the department was planning to present its evidence Friday to the Los Angeles County district attorney's office. Rose is scheduled to appear in court Monday.

joseph.serna@latimes.com