Ok, now I think I may have definitive evidence here of the officer's intent.
This seems to be the best audio/video (although for this the audio is more important) I can find of the incident.
I've just been talking w/ my sister who is a rookie (first year) cop about this. She explained that before she (and most municipalities) would taser anyone, they are supposed to say loud and clear, "Tase, Tase, Tase", and that she thought she could hear it in this video.
There is alot of backround noise, but I think i can make out those words just before the officer actually shot. The video is restricted I guess so you have to log in to youtube to see it, but if anyone listens, please tell me if you hear what I hear, because I'm not 100% sure.
And I agree w/ gio that the cop seems pretty calm before and then after he (and eveyone) hears the report from his shot, he seems very surprised. I do think it looks like a direct shot rather than a ricochet though.
I was pretty adamant that this was unexuseable no matter what the officer's intent actually was. Gun and taser certainly do not feel the same in hand, and for most police (and it looks like this guy too) they are holstered on specific sides of their body.
So while I do think this was more than likey a mistake, I do think that this cop should stand trial for (specifically) manslaughter.