Well, we don't know all of the facts. Wondering if the police person could have kicked the chair backwards, maybe suffering a minor wound to the leg. Or, could the second officer grab the wheelchair down low and pull it back and/or knock it over? a guy with one arm and one leg is not going to be getting up right away. Was a Taser available? Certainly a lot of questions with this one.
The guy in the wheelchair really needed to go to jail for trying to stab someone with a pen.