A Minnesota man who reportedly had many questions for the Internet about a banned poisonous substance has been charged with murder after his roommate died of poisoning.

Stuart Hanmer, 35, was arrested on Wednesday after an investigation into the death of Cody Ernst, 33, who died on June 22. According to a criminal complaint obtained by local news outlet St. Cloud Live, Hanmer and Ernst were roommates at a sober living facility; Ernst had been there for several months before Hanmer arrived in May.

The month Hanmer arrived, police said Ernst reportedly began experiencing strange, painful symptoms that sent him to the hospital several times over the ensuing weeks.

By the time Ernst died on June 22, his condition had reportedly deteriorated so much that he was paralyzed and put on life support, according to Ernst”s former fiancee, Cat Williams, who spoke to local news site Inforum.com. She said that the way he died was the “most horrific, awful way anybody could pass, just complete utter cruelty.”

When Ernst arrived at the University of Minnesota Medical Center on June 20, St. Cloud Police said doctors discovered “an extremely high and lethal level of the heavy metal thallium in his system.”

Thallium was used as a rodent poison and insecticide until its use was banned in the United States decades ago. Minnesota Public Radio reported that it is still used in electronics manufacturing.

According to the criminal complaint, Hanmer was allegedly very curious about it.

The criminal complaint stated that after investigators started looking into Hanmer following Ernst’s death, they allegedly found several Google searches for information about thallium. Those search terms allegedly included: “How long does it take if thallium poisons you,” “How much thallium nitrate is fatal,” “Is thallium the most toxic,” and “Is thallium metal in elemental form toxic.”

Hanmer also reportedly searched how to purchase thallium, which investigators confirmed he did — Hanmer allegedly spent $162.56 in three online transactions on 25 grams of thallium metal. The criminal complaint said Hanmer signed for a package at the sober living facility on May 14, two days before Ernst went to the hospital for the first time after experiencing an “episode of vomiting and seizure-like activity.”

The searches and the purchases were conducted in April, the criminal complaint stated. Hanmer allegedly searched more about thallium in May. Police also said that Hanmer watched a YouTube video on his phone in April and again in May about how to create thallium sulfate.

When investigators spoke to Hanmer on July 7, after Ernst’s death, he reportedly told police he and Ernst would “smoke marijuana and drink coffee together.” He claimed to investigators that he had never heard of thallium poisoning until Ernst died.

Hanmer was arrested on Wednesday following an investigation that involved local law enforcement and the Federal Bureau of Investigation. He was charged with second-degree intentional murder and booked into the Stearns County Jail, where he is being held on $4 million with no conditions, or $2 million with conditions. His next court date is scheduled for Sept. 19.