Who is "taking a knee" for David Dorn?

Chicago Tribune columnist John Kass asks, "Will anyone take a knee for retired police Capt. David Dorn? 

"Dorn, 77, was a retired St. Louis police captain. The other night, as violence raged in St. Louis, Dorn was alerted to an alarm at a friend’s pawnshop. He did what law enforcement officers are expected to do. Dorn answered the call. He tried to stop a gang of looters."

Dorn was shot to death, as much or more unjustly than George Floyd. Dorn was African-American. Didn’t his life matter, too? But there aren’t any protests for Dorn, no public kneeling in his memory. 

Leftists take a knee for George Floyd, who had a long criminal record and spent time in jail for armed robbery. But they don't for Dorn, who was not a criminal. Dorn isn't worth mention on the Black Lives Matter website.

Several other people have died as a result of the protests, looting, and violence in memory of Floyd (link). Don't their lives matter?