There have been times when a police officer has shot somebody who was armed with a knife or an airsoft gun or whatever, and I've come across as some sort of big ol' cop apologist by saying things like "How could he have known it was an airsoft gun?" or "How many times is the officer supposed to let himself get stabbed before he can put away the pepper spray and use lethal force?"
Part of it is from a certain reluctance to engage in Monday-morning quarterbacking, but a lot of it is simple self-preservation: I'd hate to have to shoot some hypothetical future knife-wielding mugger, only to have the other team's lawyer come strolling into the courtroom with a ream of printed out blog posts featuring me whining "Why didn't the cop just wrestle the knife out of his hand?"
With all that taken into consideration, and acknowledging that it is not yet Monday morning: "Blue 42! Hut, hut, hut!"
Seriously, officer? A double amputee? In a wheelchair?
I understand it was a pretty stressful situation, and that the guy had a reputation for occasionally losing his fecal matter and rolling about the place like a combination of a rabid Ghengis Khan and R2D2, but thus far the group home staff have kept him successfully tethered to Mother Earth with a toolset notably devoid of Glock 22s. Even if you really and truly thought that the pen he was waving about was an... I don't know, an X-acto knife, I guess... was going to guns the onliest and bestest solution at your disposal?
How could you have thought that would look good?