Make your preparations then head to the marked location in the parking lot. Interact with the spot to wait till nightfall to trigger a cutscene. Once done, sneak inside and kill the first guard. Get the tac-vest on the floor then sneak to the second floor where you can see an ongoing slave auction. Lob a grenade or two to kill the disgusting excuse for humans and disable Mason Carter. Subdue him to learn the location of the other human trafficking victims. (New objective) Lincoln will understably kill him immediately.
Before you leave however, you’ll be surrounded by his reinforcements. You can call your own backup or deal with them yourself. Take note that there are two sets of stairs that the enemies can take to flank you so make sure you keep using the intel view regularly to keep track of their movements. Before leaving the area, make sure to loot the huge stack of cash on the table. You don't need to kill everyone but nothing's stopping you from wiping out the remaining enemies either.