This is just the final boss fight chapter. It can be made easier by taking advantage of a couple of exploits.
During the first round use the solid structure the the right as cover as this won't be damaged by the gunfire. You can also step back a bit so that you are stood behind the cover but not technically using cover as the shotgun guys will eventually come to you.
For the second section, you can jump over the crate to trigger the enemies and then jump back so that you can take them out without the boss shooting at you.
With the final wave of enemies just remember that the extra shotgun guy will come towards you and there is a rocket launcher guy on the roof.
Also don't forget the falling storage crates QTE :P
Trophy pops when the cutscene starts.