So First of all, you will need to find the Server room in the Building which looks like this:

After a failed try to get access for Remote control with the Computer in the Server Room, one of your Teammates has to remain in the Server room and the other one has to stay in the Office, which is located on the right side of the Bank behind the Tellers. Notice: there are 2 Offices, one in the main floor and the other one in the first floor above.

To find out which Computer is the right, you have to repeatedly try hacking the Computer in the Server Room to cause a beep sound which will lead your teammate to the right Computer. Everytime when you try hacking the Computer in the Server room, a Message will appear on the Screen of the right Computer which looks like this:



The only thing you have to do then, is to hack the Computer where the Message "Operation failed" is displayed. Thats it.









Considering these Tips, you will get an Achievement, a Mask and a Weapon Modification for the Falcon Rifle for finding the right Computer with the first shot.