While giving a briefing Friday on Facebook Live, Krewson read the names and addresses of several protesters who had given her letters suggesting changes to the city budget.
"As a leader, you don't do stuff like that ... it's only right that we visit her at her home," said Democratic state Rep. Rasheen Aldridge of St. Louis, speaking into a megaphone at the protest Sunday.
During the video briefing Friday, Krewson held up a stack of crumpled papers and then read from them.
"Here's one that wants $50 million to go to Cure Violence, $75 million to go to Affordable Housing, $60 million to go to Health and Human Services and have zero go to the police," the mayor said. She then read the name of the person and their address.
Krewson listed several other names and addresses, and stated that each individual called for defunding the police entirely. As the mayor spoke, viewers commented and asked her to stop sharing demonstrators' personal information.
The video was removed later that night. Krewson apologized in a statement late Friday, saying she "did not intend to cause distress or harm to anyone."
Emails or letters to elected officials, including names and addresses, are generally considered public records but are typically released only after a formal request.
The Rev. Darryl Gray, who was at the protest Sunday, acknowledged that what Krewson did was legal, but called her actions immoral and unethical.
"Does she understand why people are angry?" Gray said into a megaphone. "If you had understood the people you were elected to serve, you wouldn't have made that comment."
An online petition calling for Krewson's resignation had about 41,500 signatures by 9 p.m. Sunday.