After completing the mission One Foot in the Grave (Act II, Mission 04), Tobias will call Aiden while in open-world mode and ask him to keep an eye out for weapon supply crates scattered across the city. Locating and scanning all nine crates will unlock a bonus mission, as well as the Spec Ops (silenced) Goblin assault rifle.
Weapons Trade Shipping Crates
SHIPPING CRATE 01
Located in the middle of Mad Mile, use the camera high up on a building across the street to find the ctOS box you need to unlock the garage door.
SHIPPING CRATE 02
This drop can be found on the island to the west of The Loop. Use the camera that is facing both the alley and the main street to find the locked ctOS box on a roof.
SHIPPING CRATE 03
Located towards the southern point of The Loop, the third crate can be accessed by hacking into the camera above the garage door, then looking across the alley.
SHIPPING CRATE 04
Located underground by the river separating The Loop and Mad Mile, look behind a stack of wooden pallets over by the stair case that leads up to the street.
SHIPPING CRATE 05
Located on the small island to the West of Mad Mile, climb the ladder onto the roof of the auto repair shop by the drop, then climb up on top of the second roof. Drop down behind the fence to find the ctOS box you need to unlock.
SHIPPING CRATE 06
Located in the southeast corner of Parker Square, cross the street, and use a camera to look at the top of the building across the street from the garage.
SHIPPING CRATE 07
This crate is located in The Wards, just south of Parker Square. Find the locked ctOS box hidden on the roof of the garage, around the back side.
SHIPPING CRATE 08
Located smack-dab in the middle of Brandon Docks, run behind the garage, and keep going until you find a big metal staircase. Climb up it and move along the roof to find the locked ctOS box.
SHIPPING CRATE 09
Found on the southern tip of the island in Brandon Docks, the locked box is located on the back side of the building next to the garage.