What kind of problems. I think it is very logical to think MB assaulted OW when he was in his patrol car and that would immediately make him a felony suspect who needed to be apprehended and arrested. It would be no different if he was trying to apprehend a felon who had assaulted someone else and they were trying to escape.
This is all that is really required under MO law for OW to be justified in using deadly force:
is justified in using deadly force only
. when he reasonably believes that such use of deadly force is immediately necessary to effect the arrest and also reasonably believes that the person to be arrested (a) has committed or attempted to commit a felony;
And for it to be an assault to a police officer the assault doesn't even have to be severe injuries. A mere assault on a police officer of any kind in any manner is still a class a felony.
IMO