The Pennsylvania man suspected of killing a Brooklyn artist at a ritzy wellness retreat in the Hamptons had been carrying on a romantic relationship with the victim for years, although she was trying to distance herself from him, according to a friend and mentor.

Police found Sabina Rosas, 33, dead in a guest room at the Shou Sugi Ban House in Water Mill, New York on Monday.

By Wednesday, they'd tracked her suspected killer, 56-year-old Thomas Gannon, to his home in Pennsylvania. He was dead of a self-inflicted gunshot wound inside.

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An undated photo of Sabina Rosas, who was found dead, murdered, on Monday, Oct. 28, 2024 in a wellness retreat in Water Mill, New York. (Provided to Fox News Digital)

"I had a sense that she wanted to get away from him," said Liz Phillips, a part-time art professor at SUNY Purchase, where she taught Rosas and hired her as an assistant.

She said she'd met Gannon, who Rosas brought over to her house twice this year, once for dinner in January and again over the summer, giving Phillips and her husband "the creeps."

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The two had been involved romantically for about four years, and Gannon funded some of Rosas' projects, the professor said.

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An undated photo of Thomas Gannon provided to Fox News Digital. (Provided to Fox News Digital)

"He came everywhere with her," she said, but she thought Rosas was getting tired of it.

She thought the younger artist was trying to distance herself from her suspected killer, and when the two traded texts over the weekend, they agreed that Rosas would visit Phillips and her husband in Queens without Gannon in tow.

Police investigate a suspicious death at the Shou Sugi Ban House in Water Mill, NY, Tuesday, Oct. 29, 2024. Sabina Rosas, a 33-year-old artist from Brooklyn, was found dead of a "violent act" in a guest room, according to authorities. (Matt Agudo/Instar for Fox News Digital)

She was supposed to visit Monday and never arrived.

Rosas was born in Tajikistan, part of the former Soviet Union, and her family fled when she was just a child to escape civil war. They bounced around Europe and Central Asia before she arrived in the U.S. in 2009, where she studied art.

Police investigate a suspicious death at the Shou Sugi Ban House in Water Mill, NY, Monday, Oct. 28, 2024. On Wednesday, police said they found the suspect, Thomas Gannon, dead of a self-inflicted gunshot wound in his Pennsylvania house. (Matt Agudo/Instar for Fox News Digital)

"She was a terrific young person," Phillips said. "I mean, I wrote her a recommendation."

In it, she praised Rosas as a hard-working and talented creative with a unique background that opened doors around the globe.

Liz Phillips speaks to the media outside of her home in Queens, NY on Wednesday, October 30, 2024. (Kevin C. Downs for Fox News Digital)

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"Sabina works hard and is developing some very exciting new projects," Phillips wrote. "She has found collaborators around the world and connects people and threads that run through cultures and can heal. Her journey is unique, and she has the potential to be a strong leader as she develops new work and venues for other artists."

Gannon was a flooring contractor based in Honesdale, Pennsylvania, according to his LinkedIn profile. His former business partner said Gannon sold his shares in their company more than a year ago, and the two haven't had any contact since then.

Phillips said he'd also designed "escape rooms" and similar structures indoors and outdoors, and he built a house in Tajikistan for Rosas, who was born there.

Sabina Rosas pictured at a recent art event during an overseas trip, just days before her murder at a spa in New York's Hamptons community. (Instagram/@ruyo.journal)

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Gannon, a divorcee, recently listed the Pennsylvania home where he was found dead for $550,000. 

"I wish he'd just killed himself and not her," Phillips said.