Let me paint a scenario different from what many are imagining, and correct at least one misunderstanding as well.
First, the shooting occurred in the employee lounge, not the sales floor. SO the comments about endangering customers are probably off-base. Employee lounge is basically the break room. THis would be in an area of the store not accessible to the general public, usually in back, and unless Costco is different from any other store around, it's probably not a large area. My guess would be 20' by 20', give or take a factor of 2. The fact that one of the officers was injured by a ricochet also suggest a smaller area with hard surfaces...ricochets loose power very quickly. That seems reasonable, but I'm willing to be shown differently and await more info before making a final judgement.
2. While there may have been more than 2 officers on the scene, customers report being told to get outside and leave the area. So some officers were involved in trying to clear the area of bystanders. It's not unreasonable that the two directly involved were the only two confronting the woman. Or, given that this was in the break room, they may have been the only two into the room when the incident occurred. We don't know.
3. As to why they all didn't use tazers, it again seems reasonable to me that, when facing an armed and possibly dangerous person, you wouldn't want everyone to be using tazers. I would expect one or more to have weapons out and trained just in case somethign unexpected happens (such as the knife wielder charges, or suddenly pulls a gun, or whatever). Basically, one to subdue and one to cover. There are police officers of various levels on the forum that I'm sure could shed light on what the current training recommends in that regard.
Now, up to this point, nothing seems to have gone wrong. Some officers (unknown number) are trying to clear the area of bystanders. Some (at least two) have gone to confront the woman in the breakroom (an area of unknown size and construction, but that would be seperated from the sales floor).
Now, assuming a 20 foot room, or even 40 foot, LTC8K6's post becomes much more relevent. Even in a 40' room, unless she was all the way on the other side, she's very close to that 21 foot mark he mentions. We don't know the original plan, which is part of the information needed (did they talk to her? What happened in that conversation?). We also don't know exactly what happened when she approached the officer with the knife (did she walk towards them? Run? Run screaming with the knife raised? Did the officer simply lie about it?) This is additional info that would be needed to determine whether or not the right course of action were taken.
However, the statements indicate that the tazer didn't work (another area of question...did it malfunction? Miss? Or, as happenes sometimes, hit but one of the darts did not penetrate through the clothing to touch skin? Or, again, was this a fabrication?).
So you have a situation that has suddenly gone pear-shaped. THe woman is within that 21 foot line, approaching, and your attempt to subdue didn't work. There is NOT time to drop or holster a gun (or a malfunctioning tazer) and draw pepper spray (unless she was simply walking).
So, assuming the woman charged them, and thr tazer malfunctioned, I can understand why events took the turn they did.
However, as I stated, I would like to know the details. If they never tried talking to the woman, or if the woman was just walking towards then and not running/charging, and so forth, then the officers messed up. Or if the woman was far enough away they would have had time to try another approach, for that matter.
Basically, I'm still open to either option. But depending on details, this may not have been a case of over-zealous officers.
Also, as an aside, you generally do NOT want to get into a hand-to-hand situation with someone weilding a knife, unless there's no other option. One of the first things to be taught in knife training is that you will get cut. Accept that at the beginning and try to limit the damage. I don't blame them for not attempting to wrestle someone with a blade.
