Kane and Lynch are actually being filmed in Dog Days
It's for a "true crime" documentary that got way out of hand. Originally, it was simply to show the public the seedy underbelly of Shanghai by showing Kane and Lynch making the arms deal with Glazer. However, Lynch's desire to ham it up for the cameras with his tough-guy antics at the beginning of the game throws the three of them (the camera guy probably being the only crew member that follows Kane and Lynch around 24/7) in way over their heads. The only reason that the camera guy sticks around with the two instead of just hopping on the next bus out of Shanghai was probably because Shangsi wanted his blood too, and so the only way for him to stay alive was to stick with the two guys with guns who seemed to know what they were doing. There's numerous little things that support this:
- Every now and then, during shootouts, Lynch will occasionally look straight at the camera with a kind of "are you shitting me?" look on his face.
- Nudity is censored out, but all the massive amounts of blood and gore are not. This is because the documentary was intended for broadcast in the U.S., where nudity has more of a taboo than violence.
- There's a few moments where even the camera guy is genuinely shocked, most notably when Glazer is taken out by the sniper and when Lynch shoots Shangsi.
- When the two are captured by the police at the end of the second act, one of the officers grabs the camera out of the cameraman's hand. Why did they let the dude keep on filming? Who knows, maybe he bribed them and/or duped them into thinking he was casting their actions in a more positive light.
- The timestamp at the top of the screen actually does show how long you've been playing/how long the camera guy's been filming. The camera guy likely switches over to a new tape/SD card when he begins focusing on Kane.
- At the end, the camera guy actually drops the camera on the ground, probably because he just realized that he's stranded in Shanghai with a couple of dead dogs and a few hundred cops who more than likely want him dead.