11/20/2014 03:21 pm ET Updated Jan 20, 2015

Firefighter Jonathan Hearn Arrested In Love Triangle Murder

(Adds that defendant wrote book about courage, other details)

By Dan Whitcomb

LOS ANGELES, Nov 20 (Reuters) - A Southern California firefighter who co-wrote a book about courage in the line of duty has been arrested along with his alleged mistress in the murder of the woman's husband, who was shot to death at a rail yard in August, police say.

Jonathan Michael Hearn, 24, and Sabrina Limon, 35, were taken into custody earlier this week on suspicion of first-degree murder and conspiracy to commit murder, the Kern County Sheriff's Office said in a written release.

A spokeswoman for the Kern County district attorney said Hearn, a firefighter in the city of Redlands, 70 miles east of Los Angeles, and Limon were expected to be charged in the case on Thursday and make an initial court appearance.

According to the Kern County Sheriff's Office, the body of 38-year-old Robert Limon was found on Aug. 17 in a BNSF Railway shop area in Tehachapi, some 100 miles northwest of Redlands.

An autopsy determined that Limon, an employee of BNSF, had been shot to death sometime after returning from the field.

During the subsequent three-month investigation, detectives determined that Hearn and Sabrina Limon were having an affair and that Hearn was responsible for the murder, the Kern County Sheriff's Office said.

Sabrina Limon is accused of conspiring with Hearn to kill her husband, it said.

According to a website promoting "Firefighter Story: Candor and Courage" Hearn is a co-author of the book, which gives first-person accounts about the heroism of first responders like himself.

Though Hearn is only 24, his biography on the website says he has "worked in the Fire Service for nearly a decade" as a volunteer, firefighter emergency medical technician and paramedic.

The biography says Hearn "places great emphasis on interpersonal development and ethics being the foundation of service" and that "his greatest moments are those spent with his family or friends."

The Los Angeles Times reported that in a Sept. 8 Facebook post, Limon wrote about her husband: "Words can not begin to express my thankful heart. Robert showed his love, compassion, hardworking skills, and genuine kindness to everyone he met."

That post has since been taken down.

It was not immediately clear if investigators believe that Hearn pulled the trigger himself in killing Robert Limon or if Sabrina Limon is accused of being present for the homicide. (Reporting by Dan Whitcomb; Editing by Mohammad Zargham)