'Dateline' Preview: 'Dark' Circumstances Surrounding Pam Zimmerman's Murder Examined By Keith Morrison

On Friday night, "Dateline" will examine the murder of Pam Zimmerman, a successful businesswoman and mother of three. Throughout the episode of the NBC crime show, host Keith Morrison will take a closer look at the circumstances surrounding her death and the investigation that followed.

Over the years, Zimmerman, who worked at a financial planning business, had developed a habit of returning home from work and turning off the lights that her children had left on for her inside their home. However, on that Tuesday morning, her oldest son, David, noticed that not only had the lights been left on, but that her room appeared dark and undisturbed.

On that same morning, a neighbor named Julie Koh happened to come and knock on their door. Upon answering, she was informed by David that his mom had not returned home the night before. After hearing the update, she decided to drive over to Zimmerman's office. According to Morrison, once she arrived, she "saw something that would lead her to call 911."

After finding Zimmerman's car in the parking lot, her husband suggested that she call 911. During the phone call, the dispatcher asked Koh if she wanted to file a missing person's report. However, she said at that time she wasn't sure that she was even officially missing.

Shortly thereafter, Ina Hess, Zimmerman's longtime office manager, arrived. At that time, she went into the office, turned the lights on, and discovered Zimmerman's body in her office. Koh then checked for a pulse, but could not locate one.

"I remember thinking, 'Everything has changed in my life right now. Everything has changed for those kids and their life will never be the same," Koh told Morrison, as seen in the preview below.

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Eventually, police determined that her death had been "no accident," as the signs indicated she had been murdered.

On Friday night, viewers will be brought inside the "dark" case as they follow the investigation.

This episode of "Dateline," called "Before Midnight," will air at 10 p.m. EDT on NBC.