Use the elevator to trigger a cutscene. After that, you’ll be in a hostile area. You can sneak around the enemies and head for the exit or you can easily stealth kill them all one by one. After reaching the exit, you have to go to the upper floor to find more enemies. You can actually go loud at this point if you want; just use your intel view frequently to prevent getting flanked by the enemies.
There’s a tac-vest and some weapons in the bedroom so don’t forget to grab those in case you need to resupply. Continue forth towards the objective marker and break through two doors. As soon as you enter, Tony will fire a rocket towards you. While in cover, you can easily disable him by throwing two grenades or just exchange gunfire with him. Once he’s down, interact with him to trigger a cutscene and to kill him.