I know OF people who were shot in the face because I've read about the violence in Chicago. I also personally know a few who have had the coronahoax virus and know OF a few who have died because they were related to neighbors and co-workers. I also know OF many others who have died from coronahoax because of reading and watching local and national news.
If you DO personally know several children who were shot in the face in Chicago, start a GoFundMe and I will make a donation. If you simply know OF them, you don't really know any more than I do from reading the news.
Anyone can know OF something because it doesn't need to be personally related to them. Do you now understand the significance of using OF in sentence structure?