A Colorado dentist has been arrested in connection with the "complex and calculated" poisoning death of his wife, local police said on Sunday.

The Aurora Police Department said James Toliver Craig, 45, was arrested on a charge of first-degree murder early Sunday morning.

Craig and his wife, who was suffering from "severe headaches and dizziness," arrived at a local hospital at about 8:45 p.m. on Wednesday night, officials said.

She was placed on a ventilator after her "condition deteriorated rapidly," police said in a statement, adding, "She was declared medically brain dead a short time later."

An investigation into her "sudden" death showed she'd been poisoned, said Mark Hildebrand, a division chief with the department.

"It was quickly discovered this was in fact a heinous, complex and calculated murder," Hildebrand said in a statement.