The first thing to do is complete the job, Rooke: The Killer.
Right, so now that you know Hightower will be there to be scared
Next thing, almost complete the final mission, up to the point where you have killed or knocked out everybody else except Hightower and Fritz Gessler.
Get to the ground floor.

Climb up the side of the building opposite Hightower, the side that has Fritz Gessler standing by the window.
Once on the roof of the building, fire your gun, Making Fritz turn around. Leap off the building and kill the sniper (If you cant do that, do what I say next VERY quickly)
Get back ontop of the building.
Slide down so that Fritz sees you and shoots the window.
If he misses (this may take a couple of tries), drop into the room quickly and point your gun at him.
Make him surrender (If you dont know how, hold your gun out and skip through the conversation).
Walk past him.

Now there are two ways to acheive this, one freezes you, the other doesnt.
1: The Freezing way
Press the button under Fritz's desk, Hightower will Immediately bolt towards the window and leap out, without smashing it, but on the downside, you cant follow him because you are frozen.
2: The Normal way
Run up to the door and kick it open with the Gatecrashers, same thing will happen but you wont freeze up, if you try to follow him down to the ground he will be gone (I say he went to Hawaii, but you can decide what you think)

Thank you for reading this guide.
Now you can acheive the status of "surprising"!