Dunno. I’d be the first to slam the police for exceeding their powers, but you can’t be sure what was going on.
It was more than a mild coincidence someone happened to be filming what would under any other circumstances (no fatality occurring) been quite a pointless bit of footage. The chap’s demeanour was one of apparently calculated insouciance and what seemed to be an unwillingness to do as directed.
While the cops obviously didn’t need to shove him, you have to wonder if there weren’t some verbals going on. Again, no excuse, but you can see how it might happen.
It’s quite possible he was an agent provocateur, and if so, he certainly earned his crust that day, but even if that was the case, there was no immediately apparent justification for the police action. The correct terms of engagement are quite clearly laid down in police procedures manual. Shoot the b!ugger, then retrospectively piece together a story that absolves them of any blame, while highlighting the need for greater vigilance from the population as a whole in supporting the police in their on-going fight against terror, drugs, human trafficking etc.