You know that the Daily Mail is a hated, right wing, sensationalist pile of crap that most people wouldn't wipe their ass with for fear of making it dirtier, right?
They don't know who killed him, you don't know that whoever killed him was yelling Black Lives Matter. That's all speculation on your part.
"Dorn had been passionate about helping young people, Powell said, and he believed his father would have forgiven those behind the violence and tried to talk to them."