Johnson, who is working with a lobbying group that supports ShotSpotter, addressed the Community Commission for Public Safety and Accountability Wednesday night and spoke about ShotSpotter.
The City of Chicago plans to stop using the gun detection technology on Sept. 22.
Johnson called that choice mind-boggling.
"Everything the city has to bear, brings to bear to stop gun violence in this city, we should be willing to do. Everyone in this auditorium deserves to feel safe and to be safe," he said.
The city declined to respond to Johnson's comments.