James Toliver Craig, 45, was arrested early Sunday morning by the Aurora, Colorado, police department.
CNN  — 

A Colorado dentist is accused of fatally poisoning his wife by putting arsenic in her protein shakes after ordering it online and making a number of suspicious internet searches in the weeks leading up to her death, including “how to make poison,” according to an arrest warrant affidavit.

James Toliver Craig, 45, was arrested Sunday and preliminarily charged with first-degree murder after his wife, Angela Craig, 43, died after being hospitalized for severe headaches and dizziness, the Aurora Police Department announced.

Investigators allege James Craig “has shown the planning and intent to end his wife’s life by searching for ways to kill someone undetected, providing her poisons that align with her hospitalized symptoms, and working on starting a new life” with another woman, the affidavit says.

The affidavit says Angela Craig died after going to the hospital for the third time in March. After she arrived the final time, she had a severe seizure, was placed on a ventilator and was declared medically brain dead soon after, it says.

Angela Craig died Wednesday after reporting to the hospital for the third time this month, according to the affidavit. After she arrived, she had a severe seizure, was placed on a ventilator and was declared medically brain dead soon after, it said.

In the weeks before her death, James Craig used a computer at his dental practice to research multiple “undetectable poisons” and make internet searches including “how many grams of pure arsenic will kill a human” and YouTube searches for “how to make poison” and “Top 5 Undetectable Poisons That Show No Signs of Foul Play,” according to the affidavit.

CNN has been unable to determine if Craig has an attorney.

The husband also used a new email account to order arsenic online, the affidavit says.

On March 6, two days after the package of arsenic was delivered to the Craigs’ house, Angela Craig went to the hospital and reported that she was dizzy, could not focus her eyes and felt her body was responding slowly, according to the affidavit, which notes the conditions are consistent with some symptoms of arsenic poisoning.

That day, Angela texted James Craig, “I feel drugged,” according to screenshots of what the affidavit said were texts between the pair.

The husband responded, “Given our history I know that must be triggering. Just for the record, I didn’t drug you. I am super worried though. You really looked pale before I left. Like in your lips even.”

According to the affidavit, Angela Craig’s sister told investigators the couple’s marriage was tumultuous and she was told by Angela that James Craig had previously drugged her because he was planning to attempt suicide and didn’t want his wife to be able to stop him.

Also on March 6, James Craig ordered oleandrin, a toxic plant extract, but the shipment was “intercepted by FedEx” at the request of investigators and never delivered, according to the affidavit.

His wife was hospitalized again from March 9 to March 14, during which time James Craig ordered the highly lethal chemical potassium cyanide, which was delivered to his dental practice, the affidavit alleges.

While Angela Craig was hospitalized for the final time on Wednesday, one of her husband’s business partners told a nurse about James Craig’s delivery of potassium cyanide at their medical practice, noting there was no need to have the chemical in the office, the affidavit says. The nurse then reported this to police, setting off the investigation into Angela Craig’s death.

The husband told the Department of Human Services that his wife had been suicidal and “had told fellow employees that his marriage was failing, and he was in financial turmoil,” the affidavit says. The document notes that none of the people interviewed by investigators suggested Angela Craig had expressed suicidal thoughts.

After Angela Craig’s death, her sister told investigators James Craig told her he did not want an autopsy to take place.

“James said he felt if they couldn’t figure out what was wrong with her when she was alive he wouldn’t let them poke her more when she was dead,” reads the affidavit.

James Craig had his first court appearance Monday and the charges are expected to be formally filed Thursday, according to Colorado Judicial Branch Court Executive Shaun Clark. He is being held without bond and is not allowed to have contact with his six children, CNN affiliate KUSA reported.