WHY ??? What's going on, why are the flags hanging at half mast? Is it the time?

https://www.senate.gov/general/capcam.htm

Only people mentioned by @HTGthelapis in this post can reply

In response HTG TheolddoG to his Publication

Should be for Rush, but it's not. Biden ordered flags at half-staff to mark 500,000 COVID deaths.
https://news.yahoo.com/president-biden-orders-flags-half-212229567.html