As private Facebook groups continue to flourish on the social media platform, some have become known sources of misinformation. As a tragic story out of Colorado shows, sometimes that misinformation can become deadly.

The group “Stop Mandatory Vaccination” has over 139,000 members, and much of the discussion on its various comment threads includes people asking for health advice. One of those people was the mother of a 4-year-old boy who passed away from the flu this week, according to NBC News.

In her post, the woman wrote that two of her four children had been diagnosed with the flu and that she had been given a doctor’s prescription for the antiviral drug Tamiflu, which she decided not to pick up. Her 4-year-old had not been diagnosed yet, but he was running a fever and had suffered a seizure.

According to NBC News, none of the 45 comments on her post encouraged the woman to pick up the prescription and treat her children with it. Four days later, her son was dead.

In past posts to the group, the woman indicated that she chooses not to vaccinate her children for the flu.

Speaking to NBC News, University of Texas at Austin researcher Kolina Koltai said that groups like the one the woman sought out advice in have become dangerous echo chambers.

“These communities have become a haven or resource for parents and for women to connect with others and ask for help,” Koltai said.

A GoFundMe that was set up for the boy before he passed is still active.

Featured image via KKTV