I have "unsnapped" when I was riding shotgun on a drving citation. My partner was at the driver's side window and I was on the passenger side and far enough away and in a drainage swale so I could see the driver from shoulders to waist. The driver suddenly dropped his right hand toward the space behind the console, and (a)my heart stopped; and (b) I unsnapped my sooper-dooper Level III holster. Then his hand came up with a microphone it it.
In other words, I tend to wait for some overtly suspicious or aggressive behavior or the sight of a weapon. (I haven't seen the video - dial-up here.)
That's my problem, and my point, I'm not going to take the word of some ambulance chasing lawyer before I hear or see the other side of the story.
I assume this holster was not for a taser, which explains your hesitancy to draw and fire. Perhaps a taser is just a little too easy to use.
If I'm confronting some whack-job and I've got the authorization to use a taser in circumstances like these ... I don't know ... all kinds of bad things can happen quickly. Let me just say that, although there may have been other and better ways to handle this person (especially knowing what we know now), I can understand his use of the taser.