Maybe the suspects wanted to go down with a fight.
Thus they hung around the area waiting on that fight.
Has that thought occurred to you?
The suspects hung around so they could qualify for their 72 Helen Thomases.
They could have stayed in the building and killed lots more people and they shot it out with an army of cops.
No their actions say that they intended to get away. They were in and out in minutes.
My guess is that if they were terrorist they have or had intensions to go on to kill again in a similar fashion as long as possible.