MINOT, ND (KXNET) — A woman accused of fatally poisoning her boyfriend in North Dakota may have been hoping to steal his sizeable inheritance, according to new details.

Ina Thea Kenoyer, 47, was arrested Monday and charged with Class AA felony murder in connection with the September death of a 51-year-old Minot man.

An arrest affidavit indicated that the boyfriend, identified by Minot police as Steven Edward Riley Jr., was in line to inherit over $30 million and was planning to leave Kenoyer, whom he had been dating for about 10 years.

On Sept. 3, Riley had planned to meet a lawyer at an airport to finalize the transaction, according to the affidavit. Kenoyer and many of the man’s friends accompanied him to the airport, but friends began to notice his health rapidly decline and him acting as though he were drunk despite not drinking any alcohol, the documents said. He also experienced stomach pain and began having trouble walking.

Friends say they tried to get Riley medical treatment, but Kenoyer insisted that he was suffering from heat stroke and just needed to go home and rest. Soon after, he began vomiting and could not walk on his own, authorities said. Friends said they became very concerned, but Kenoyer told them that she had medical training and insisted the boyfriend was suffering from heat stroke.

The following morning, a friend went to check on Riley but was told by Kenoyer that he had gone to a clinic. The friend visited every clinic and ER in Minot but could not find any record that he had been treated, the documents said.

Later that day, first responders were dispatched to Riley’s address for a report of an unconscious male and transported him to a local emergency room. His condition was so severe that he was flown to a hospital in Bismarck, but he never regained consciousness and died on Sept. 5.

A coroner, who was informed by the man’s friends that Kenoyer had made comments about poisoning her boyfriend with antifreeze in the past, ran tests for ethylene glycol (a key ingredient in antifreeze) that came back with toxic levels of the substance.

An autopsy confirmed he had died of ethylene glycol poisoning.

Investigators later searched Kenoyer and Riley’s home and found several items of note, including an old Windex bottle without a cap that contained a bright green liquid as well as a glass Coors Light bottle and a plastic mug both containing the same liquid. The liquid was suspected to be antifreeze.

Kenoyer told investigators that her boyfriend had been drinking alcohol all day on Sept. 3, claiming he had heat stroke. Bloodwork ultimately determined Riley had no alcohol in his system after he died.

Kenoyer also admitted that she was aware of Riley’s inheritance and said she had planned to split it with his son now that he was dead, believing she was entitled to a portion of the money as his common-law wife, investigators said. She became upset when they told her that North Dakota does not recognize common-law marriage, according to the arresting documents.

The suspect, meanwhile, was providing scenarios to investigators to explain how Riley could have potentially ingested antifreeze, such as if his cigarette fell into the antifreeze in the garage and then he smoked it. She also began telling them that Google says the symptoms of heat stroke can “mimic poisoning,” according to the documents.

Kenoyer ultimately admitted that she had put antifreeze into some sweet tea she had made for her boyfriend on Sept. 3, according to the arresting affidavit.

She is currently being held in the Ward County Detention Center with a preliminary hearing scheduled for Dec. 7.

“This case was extremely complex,” said Investigations Commander Captain Dale Plessas in a press release. “Thank you to everyone who provided us with information that helped our investigators piece this together.”

This investigation is still ongoing.