http://www.foxnews.com/us/2014/08/20/missouri-cop-was-badly-beaten-before-shooting-michael-brown-says-source/

https://tinyurl.com/pc2g4ye

[..]

“The Assistant (Police) Chief took him to the hospital, his face all
swollen on one side,” said the insider. “He was beaten very severely.”
[...]

"Wilson suffered a fractured eye socket in the fracas, and was left
dazed by the initial confrontation, the source said. He is now
"traumatized, scared for his life and his family, injured and
terrified" that a grand jury, which began hearing evidence on
Wednesday, will "make some kind of example out of him," the source
said."

“You may engage a threat with enough force that is reasonably
necessary to defend against that danger,”...

(fight fire with fire, meet force with force)

Justified Homicide! in my view.