Remember that the shotgun is always leaning against an object such as a table, chair, fountain, flowerpot, tree, railing, wooden pillar, etc. And you should find the combat shotgun at one of the mentioned locations. You need to go to specific locations, which we have covered below. There are no major requirements for this shotgun. There is a fixed number of locations, but the shotgun can only spawn at one location randomly. The Combat Shotgun is a powerful shotgun you can find in a random spot inside El Rubio's compound during the Cayo Perico heist finale.
The pistol remains with you once you acquire it from the office. You can later purchase the ammo for the Perico Pistol from any one of the nearest Ammu-Nation. Open it up using the small key, and you will obtain the gold Perico Pistol.
Once you have the small key from the passed out guard, you will need to use it on the locked drawer in El Rubio's office during the Cayo Perico heist finale. You will see a blue dot appear at the locations shown below indicating a random event, just like any other random event in GTA Online. Once you acquire the weapon once, it will be available to purchase at the nearest Ammu-Nation. The key is used in El Rubio's office during the Cayo Perico heist finale to obtain the pistol.