What I don't understand is that he says he gave the film to the police and then posted it to Facebook. Surely they warned him not to? (Evidence in an ongoing criminal investigation, etc.) And if he had his own copy of the film to post to Facebook, then he must have copied it to his computer before giving it to the police.
Also, again: the mere fact that they stopped the car and got out to shoot the guy at all. NB, they didn't just slow down and shoot him in passing; they stopped the car (quite unnecessarily), at least 20 yards away (quite unnecessarily), then both of them exited the vehicle (quite unnecessarily), strolled up to him, shot him at point-blank range, and then strolled back. They might have been picking up a six-pack from the 7-11.
I'm sorry, but that is not a getaway. They were in no hurry at all. And the already injured policeman posed absolutely no threat to their "getaway". And they had just spent "5-10 minutes" carrying out a very noisy massacre in the centre of Paris at 11:30 am on a workday.
Yet there they are, in a narrow side-street with a bend in it, with every reason to expect heavily-armed SWAT teams rushing in from both ends of the street at any moment -- or at least for the cops to erect barriers to prevent their escape.
And while they were so coolly and casually wasting time like this, there just happened to be someone filming them? Directly opposite? With no cars or trees happening to obscure his view?
It's possible, certainly.