How do you rob a store?

In Saints Row: The Third, one of the challenges is to rob X amount of stores, but every time I aim a gun to the store owner and/or hold them hostage, it just sets off an alarm....

Am I doing something wrong or does it have to be unlocked via respect the same way mugging is unlocked?

Solution 1:

Walk into a store that you can buy from like rusty needle or friendly fire and aim your gun at the person behind the cash register and hold your aim there and if they move follow them with your aim steady and they will give you the money or put it on the counter or floor.

So the thing is you must keep aiming at him or he will set off his alarm.