No way that 5 officers can't detain one man without shooting him. That being said, let's get the obvious questions out of the way. If he was being placed under arrest or being legally detained, he should have been cuffed. That's first and foremost. The part that you don't see would be, and should be, the part where the police officers pat down the guy and check him for weapons/drugs/drug paraphernalia, which is SOP in an arrest/detainment. Nonlethal force before lethal force: this is instilled into every training regiment. Lethal force is the last option. Add these things together with video and witness testimony, and you have a clear cut case of the police fucking up. Again.
And yes, I have been in that situation, quite a few times, so I know that this split second decision to use NONLETHAL force should have been an easy and clear one, what with all the training that the officer has gone through. Sounds like a case of another trigger-happy cop who was way too freakin panicky and decided that a guy held by one cop and watched over by another, with two more watching the crowd with guns drawn, just wasn't enough to make him feel safe.