The toxic ingredient the Arizona couple consumed was not the medication form of chloroquine, used to treat malaria in humans. Instead, it was an ingredient listed on a parasite treatment for fish.

The man's wife told NBC News she'd watched televised briefings during which President Trump talked about the potential benefits of chloroquine. Even though no drugs are approved to prevent or treat COVID-19, the disease caused by the coronavirus, some early research suggests it may be useful as a therapy.

"We were afraid of getting sick."

The name "chloroquine" resonated with the man's wife, who asked that her name not be used to protect the family's privacy. She'd used it previously to treat her koi fish.

"I saw it sitting on the back shelf and thought, 'Hey, isn't that the stuff they're talking about on TV?'"

The couple — both in their 60s and potentially at higher risk for complications of the virus — decided to mix a small amount of the substance with a liquid and drink it as a way to prevent the coronavirus.

"We were afraid of getting sick," she said.

"I started vomiting," the woman told NBC News. "My husband started developing respiratory problems and wanted to hold my hand."

She called 911. The emergency responders "were asking a lot of questions" about what they'd consumed. "I was having a hard time talking, falling down."

Shortly after he arrived at the hospital, her husband died.