We've Only Just Begun
Head to the Broken Shillelagh. Mission will be complete after the scene.
Hit the Powder Room
Head to the target location to start the mission. Head to the back door and start killing. Go inside the warehouse and go through the break room to find the objective marker. Head there and you'll face a mini-gun wielding brute. Kill it and some guards then take the door leading to the catwalk.
Something angry.... with a mini-gun
Continue clearing the catwalk until you reach the office. Once there, Shaundi will try to download data from the PC so you need to hold off your position until it is complete.