Olympic gold medalist Shawn Johnson just revealed her children's school was placed on lockdown as the Nashville shooting went down nearby ... and while her two kids are safe and back home, she's devastated for the families who can't say the same.
The former Team USA star shared the terrifying update on Monday ... saying, "I haven't been able to catch my breath since reading the news and getting a call from our school that they were on lockdown as well given the news. Shaking. Crying. Heartbroken. Horrific."
"Our babies are now home with us.