Also check Mounted Gunner Medium.
The Mounted Gunner has been trained specifically to man and defend mounted guns. Due to the strictly specialized functions in the Helghast army, he is the only Helghast type that is allowed to use the mounted machine gun. Though this gives the Gunner a lot of firepower, a machine gun nest can be outflanked, leaving the Gunner exposed.
The Mounted Gunner is a specially trained Assault Trooper that has taken up a position on an Emplaced StA3 LMG. The fire from the LMG is deadly, even at a distance, so you'll always want to try and take them out from afar. Seek crouching cover and PS the Gunner for a headshot. Alternatively, use the VC9 or grenades to take him out. If you use the VC9, do not aim for the Gunner himself as the shielding of the Emplaced gun will block the rocket. Instead, aim to the left, right, or above him and try to hit the walls near him so that the splash of the explosion will take him out.
If you can flank the Mounted Gunner and get close, he will release the Emplaced gun and resort to the standard attacks of the Assault. When you come up behind them, they will often not see you and will continue firing the LMG forward. This makes it very easy to knife them in the back for a fast kill. Always look for a way to flank them and get close for Melee attacks.
First Appearance: Corinth River: Corinth Sands
There are 2 Mounted Gunners as confirmed by the "Killzone 2 Fansite Kit", also known as Unlockable 4 on killzone.com, however this is the only Mounted Gunner which appears in the Killzone 2: Collector's Guide to Campaign and Warzone.
You can melee any of the 2 Mounted Gunners for the Safari Hunter trophy.