After 30 years on the job (including SWAT and being an instructor), I can tell you that this was a bad shoot for sure. Yeah, the guy was armed with a knife (as stated in the video), but he was NOT attacking the officers nor citizens. He was simply refusing commands to not enter the store. That is NOT cause to be shot in this specific incident. Personally, I have never experienced bad, corrupt cops over my time (thankfully) ... but they exist.
Based upon the information provided and the video, the cop that shot the suspect should be arrested, charged and subsequently fired for sure.
By the way, the idiot that created the YouTube video misspelled "SHOPLIFTING". Just a note. It matters WHO creates and presents such digital media (as it has been pointed out that the media creates and presents certain false issues these days).