On the main page, the 'Sawed off Shotgun' is similar to the Stubby Shotgun of Vice City.
It's based on a Mossberg 500.
The shotgun the SWAT team is holding in the artwork is a SPAS 12.
The shotgun being held from the car along with the Desert Eagle,
Is a Remington 870. Like the shotgun found in the police car in Other GTA's.
This one doesn't have the wodden stock.
Also, the Desert Eagle has a slightly longer barrel than standard giving it the option of a Silencer..
Perhaps this will become the Silenced Pistol?