A Colorado dentist accused of fatally poisoning his wife in a “complex and calculated murder” was arrested over the weekend, officials announced. 

James Toliver Craig, 45, a dentist in Aurora, was arrested Sunday, four days after he drove his wife, 43, to a local hospital Wednesday evening because she was complaining of “severe headaches and dizziness,” the Aurora Police Department said.

After arriving at the hospital, the wife's condition “deteriorated rapidly.” She was placed on a ventilator in the ICU and “she was declared medically brain dead a short time later,” authorities said.

An investigation was launched into her suspicious death and determined she was poisoned. It's not clear what she was poisoned with.

A warrant for first-degree murder was obtained early Sunday morning, shortly after doctors made the decision to take the wife off life support.

Craig was booked into jail at 2 a.m. Sunday on a charge of first-degree murder. It's not immediately clear if he has a lawyer.

“When the suspicious details of this case came to light, our team of officers and homicide detectives tirelessly worked to uncover the truth behind the victim’s sudden illness and death,” Investigations Division Chief Mark Hildebrand said.