The Murder of Rebecca ‘Becky’ Koster

Written By Kiley Baumgartner

Warning, this case discusses murder and dismemberment.

For this case, I watched an episode of Ice Cold Killers. It’s season 4 episode 2, ‘Bitter Blade.’

A 24-year-old woman disappears after a night out.

Background

Rebecca ‘Becky’ Koster was born on June 12, 1985. She lived in Medford, New York on Long Island, with her parents, Larry and Barbara, and her brother. Rebecca’s goal in life was to become a nurse like her mom. She worked as home healthcare aid, and loved the work she was doing.

Rebecca was described as sweet, warm and welcoming to everyone. She was also very reliable, hardworking, but enjoyed going out when she could.

Rebecca Koster

The Disappearance

On December 3, 2009, Rebecca went out with her best friend, Nicole, her new boyfriend, Dan Mayor, and some other friends.

Rebecca’s friends said that Rebecca received a lot of attention when they went out. Rebecca was very trusting, and sometimes too nice. (This is in no way victim blaming, but how her friends described her in the episode).

Around midnight, Nicole wanted to leave, but Rebecca decided to stay behind. Nicole said Rebecca walked her out to say goodbye, and was the last time she saw her.

Rebecca was dropped off at home by her boyfriend and friends. However, Rebecca’s dad, Larry received a phone call from her boss around 6am. Rebecca hadn’t shown up for work, which wasn’t like her at all.

Her parents discovered that Rebecca’s bed hadn’t been slept in, and her purse and ID were found inside the house. Rebecca’s phone went straight to voicemail.

The First Suspect

Rebecca’s loved ones immediately made missing persons flyers and posted them around town. Rebecca had lived in Medford her whole life, so everyone knew her.

Later that night, Larry called the Suffolk County police. He was notified that Rebecca was an adult, and had only been missing for 12 hours. The police were able to use a locater app to track Rebecca’s phone.

Around 2am, Rebecca’s phone had pinged off a tower in a town about 12 miles from Medford. Rebecca's loved ones drove there, and went door to door with her photo. It was a dead end, and no one had seen her.

The Suffolk County police did end up launching an investigation. The first theory was that Dan had something to do with Rebecca’s disappearance.

Rebecca’s mom, Barbara, became suspicious when Dan had asked her if Rebecca had been seeing someone else. He would maintain his story during the investigation that he had dropped her off at home.

The Text Messages

The police kept Dan in the back of their minds as their prime suspect. They also went to the bar that Rebecca and her friends had been to. No one had seen anything suspicious.

A piece of video surveillance from the bar emerged. In the video, Rebecca was seen alone looking like she wanted to go home. Several men were seen walking up to her that night. One man had even used her phone, and added his number into it. From the video, it looked like Rebecca wasn’t interested, but was friendly.

Rebecca’s loved ones hoped that Rebecca was alive and would come home. However, their fear escalated when crime scene investigators came to the house to collect DNA and hair samples.

Three days after Rebecca disappeared, Barbara also received a text message from “Rebecca.” The message said that Dan had her tied up in a basement. Barbara and Larry rushed to his house along with the police. Sadly, there was nothing found in the basement. Dan said that he had dropped Rebecca off.

Barbara received one more message from “Rebecca.” This message told Barbara not to tell about the messages or she would be killed. The phone was pinged, and led the police to an industrial area on the other side of the island. Again, there was nothing found.

A Monster

At first, Barbara had believed that Rebecca had been trying to reach her. But, the more she thought about it they just seemed off. There were no misspelled words, and the phone was never answered when Barbara tried to call it. Barbara also found it odd that Rebecca wouldn’t have been able to at least try to call 911.

The police obtained Rebecca’s phone records, and learned that she had received several calls on the night she disappeared. The number was traced to a burner phone with a Boston number, so unfortunately, there were no records for this phone number.

Just 5 days after Rebecca disappeared, Larry received a phone call from the police. Rebecca’s loved ones were notified that Rebecca had been the victim of a homicide.

Rebecca’s badly burnt remains had been found in North Stonington, Connecticut. On December 4, a passerby had seen a brushfire. The fire department was called, and when the put out the fire, they found the remains. The remains were wrapped in a blanket, plastic, and were taped with duct tape. There were also signs of partial dismemberment.

The Connecticut State Police checked recent missing persons cases, and strongly believed that the remains would be a match to Rebecca. They were correct, and it was confirmed when Rebecca’s dental records were used.

Rebecca’s autopsy revealed that her cause of death was stab wounds to the liver and neck. The killer had also attempted to remove any identifiable features. Rebecca’s ears and nose were removed because she had piercings. Her ankle and back tattoos had also been removed.

Rebecca had been killed almost right away. Barbara had been received messages from Rebecca’s killer. It’s also believed that the killer had found out about Dan through old messages. Dan was cleared as a suspect.

The Arrest

The police received a phone call that a fingerprint had been recovered from a piece of partially burnt duct tape. It was a miracle as everything else had been ruined by the fire.

The fingerprint belonged to a man named Evans Ganthier, a 30-year-old from Long Island. Evans was the identified as the man from the bar that had put his number into Rebecca’s phone.

On February 8, 2010, Ganthier was arrested. He admitted to being with Rebecca that night, but didn’t kill her. He would go on to tell the police a completely fabricated story.

He claimed that he had called Rebecca, and that she got into his car. He said that while they were in the car, Rebecca began coughing and foaming at the mouth. Instead of taking her to the hospital, he took her to his house to give her water.

His story became even more farfetched when he said that they entered through the garage. He claimed that Rebecca had tripped over a dumbbell. However, her autopsy never revealed any blunt force trauma. It showed that her cause of death was stab wounds to her liver and neck.

Ganthier admitted to repainting his garage and floor, but not to killing Rebecca.

At trial, it only took the jury a few hours to deliberate. He was found guilty, and sentenced to 25 years to life. There was no clear motive in this case, but it’s believed that Ganthier decided he would kill Rebecca after meeting her at the bar.

Evans Ganthier

Kiley Baumgartner
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