Did One Of The Men In Her Life Gun Down A Single Mom In Her Office?

Pam Zimmerman had always been a devoted mother, so when her three high school-age children woke up on Nov. 4, 2014 in their Bloomington, Illinois home and realized their mother had never come home the night before, they knew something was wrong.

“Her bedroom was dark and it looked like no one had been there,” her son David Zimmerman told “Dateline: Secrets Uncovered,” airing Wednesdays at 8/7c on Oxygen. “My mind was probably a million different places. I thought it was the weirdest thing. I was like, ‘All right, she didn’t come home so where is she?’”

The single mom — who had gotten divorced two years earlier — was a successful financial planner, newly engaged after a whirlwind romance and enjoying a full life with friends and family before that mysterious morning.

The teenagers' concern for their mom only grew when Pam’s neighbor and close friend Julie Koh knocked on the door early that morning, looking for their mother. Koh had gotten a call from Pam’s fiancé, Scott Baldwin, who lived several hours away. He too had been worried when he couldn’t reach Pam.

“He said, ‘I haven’t heard from Pam. I’m really worried I’ve been trying to reach her since last night. She’s not answering,” Koh recalled.

Koh convinced the three teenagers to head to school, while she promised to find out where Pam was. She jumped in her car and headed to the office where Pam had her own financial planning business. She found Pam’s car in the parking lot and called 911 before spotting Ina Hess, Pam’s longtime office manager, in the parking lot. Together the two women went inside Pam’s office and made a grisly discovery.

Pam was lying curled in the fetal position on the floor near the front desk. Koh, a nurse, rushed to check Pam’s vital signs, but it was too late. Her beloved friend was gone.

“I remember leaning down and 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 "Dateline" correspondent Keith Morrison.

A medical examiner would later determine that Pam — a smart, ambitious woman who was quick to make others feel valued and loved — had been shot four times.

“There were two bullet wounds in her chest, in the front of her body. There was one bullet in her temple and then there was one bullet wound in her back,” veteran crime reporter Edith Brady-Lunny said.

Police discovered Pam’s cell phone and wallet were missing, along with an office calendar that tracked appointments, but the cell phone and wallet were later found intact along the side of a road, leading investigators to believe the items had been taken in an effort to stage the crime scene.

Detectives suspected it had been more likely that Pam had been targeted by someone she knew and focused on three men in her life: the last client she ever saw before her death, her new fiancé, and her ex-husband, Kirk Zimmerman.

When Hess had left the financial planning office the day before, Pam had been meeting with Eldon Whitlow, a long-time client. Whitlow told police there had been nothing unusual about their meeting and said he left around 5:40 p.m. before heading to dinner with his girlfriend.

Police were troubled when they learned that Whitlow had owned a 9 mm handgun — the same type of weapon used to kill Pam — but after seizing the weapon they determined it had not been the one used in the crime and he was dismissed as a suspect after his alibi checked out.

Then there was Baldwin, Pam’s new fiancé. The couple had celebrated their impending nuptials just days before her murder after a short courtship, but her children were troubled by his behavior in the days that followed her death.

Just a week after she died, they said he took the teenagers to dinner and made a troubling announcement.

“He was like, ‘I had nothing to do with this and I need you guys to understand, like, I have to move on,’” David remembered.

Detectives also learned that at the time of the murder, Baldwin had been texting and talking with other women, but they determined that on the night Pam was killed, he had been at his home a few hours away from the crime scene.

Their focus then shifted to Kirk. Although the couple had been divorced for several years, Pam’s close friends and family said there was continued tension between the pair leading up to the murder and remembered that Pam even told others that she was afraid of her ex.

 “She would always say if anything ever happened to her, he should be the person we should look at,” her cousin Vicki Sartori said.

Just days before she was killed, Pam had sent a letter through FedEx demanding that Kirk pay her approximately $4,000 in money she said he owed her for the children’s medical and school expenses and threatened to take him to court if he didn’t pay within five days.

Pam’s brother Larry Alexander also told “Dateline” that Kirk had always dreamed of retiring at 55 years old, but that the financial strain of the divorce may have made that goal unattainable.

However, the couple’s children staunchly defended their father and said the divorce had been drama-free.

“I know anybody is capable of doing anything, but we would know. We’re his kids, he lived with him,” daughter Rachel Zimmerman said.

Investigators disagreed and arrested Kirk for his ex-wife’s murder after discovering gunshot residue on the gearshift of his car.

Although Kirk had insisted that he had been home the night of the murder, his girlfriend, Kate, told police she had gone to the home that night for a date and Kirk hadn’t answered the door.

In court, prosecutors focused on the gunshot residue, an eyewitness who claimed to have seen Kirk at the office building that day, and data from his car that they believed showed he had been in the area of the fatal shooting the day Pam was killed — although his phone showed he had been home.

They believed he killed his ex-wife because of their ongoing financial disputes.

“He knew that as long as she was still alive, he was going to go broke,” Assistant State’s Attorney Brad Rigdon argued in court, according to “Dateline.”

But Kirk’s defense attorney dismissed the prosecution’s theory that there had been any financial motive at all.

“Kirk had a full pension, guaranteed for life, which he could have taken at any point and time,” John Rogers told “Dateline." “He was making $95,000 working for State Farm. He had in excess of $240,000 in his 401k.”

They called a defense expert witness who agreed that there had been gunshot residue on the gear shift but suggested it had been too much to have found its way there naturally. They also called a witness of their own, who reported hearing gunshots around 5:10 p.m. that evening, suggesting that Pam could have been killed when Whitlow was still in the office.

After deliberating for a day and a half, a jury found Kirk not guilty.

“It was just this huge relief just to know that our dad wouldn’t be going away for something he didn’t do,” his daughter Heidi Zimmerman would later say.

The children’s hope now is that their mother’s killer will some day be brought to justice.

“I obviously hope that they do catch whoever did it, but I wouldn’t be surprised if they don’t,” Heidi said.

While Pam’s children continue to believe in their father’s innocence, Pam’s other family members were devastated by the verdict.

“There’s still a lot of anger,” Alexander said.

For more on this case and others like it, watch "Dateline: Secrets Uncovered," Wednesdays at 8/7c on Oxygen or stream episodes here.