A 26-year-old man was sentenced Wednesday to life in prison for killing a retired St. Louis police captain as he tried to stop a pawn shop from being looted during racial injustice protests two years ago.The St. Louis Post-Dispatch reports that the life term was mandatory after Stephan Cannon, of Glasgow Village, was convicted in July of first-degree murder in the death of 77-year-old David Dorn.His death drew attention nationwide because it occurred amid protests across the country in response to the murder of George Floyd by Minneapolis police.Across St. Louis that night, Dorn and four officers were shot, authorities were pelted with rocks and fireworks, and 55 businesses were burglarized or damaged."Our father was a good cop, but more importantly, he was a good man," his daughter, Lisa Dorn, said to the court."