If you are planning for an aggressive approach, then the Aggressor and the Conspirator are good options. But, if you want to sneak your way in, then the Crack Shot is recommended. Do not forget to buy the suppressors for your weapons should you choose to go with the sneak approach.
You will be asked to go to one of the skyscraper buildings to retrieve the unmarked weapons. You can either enter the building head-on or use the roof access to enter the office level directly. We recommend using the roof access for easier escape later on.
Once inside, clear the office of all the guards. You need to look for a secret weapons locker inside the office.
The weapons locker is hidden behind a secret wall compartment that you won't be able to open up on the first try.
You must hack the laptop on the table to open the locker.
Once again, the hacking system isn't anything new. It is similar to the one seen during the Diamond Casino Heist. You need to find the matching number sequence and select it to hack successfully.
After hacking the laptop and retrieving the weapons from the locker, exit the building (preferably via the roof if you entered that way) and deliver the weapons back to your Kosatka submarine to complete the mission. Remember to purchase suppressors for GTA$5,000 from the heist planning screen if you intend to use a stealth approach.
With your weapons secured, you might consider weakening El Rubio's forces. Head back to the main Cayo Perico setup guide or check out the Disruption Missions Guide for optional ways to make the finale easier.