Possible in theory, but you're not allowing for the unexpected and uncontrollable.
In the famous "L.A. Bank Robbery Shootout" a few years ago, the perpetrators:
- stayed only the allotted time in the bank (they'd actually logged and recorded LA police response times, and had a countdown stopwatch sewn to their glove)
- had successfully robbed two banks previously and gotten away clean
- weren't 'busted' by someone in the bank tripping an alarm, either silent or otherwise
- handled the crowd very decisively, to the point of cold-cocking one old lady who wasn't moving (couldn't move) as fast as they wanted her to. Nobody challenged them or gave them grief, and they were dealing with over forty people inside. VERY good control of the room.
- weren't given away by their car
- weren't "hopped up" as is often said. They had "drugged up" somewhat, true, but not on coke, meth, or other speed. They intentionally injected themselves with low levels of phenobarbital, to calm the nerves, not get cranked up, for the job.
Sounds like they did everything right, so how did they get caught? Chance. Pure, simple, unforeseeable random chance.
A police cruiser just happened to pass by right at the "wrong" three seconds or so as they were exposed between their car and the bank's door. No way to plan for that, and it got them both killed.
Life is messy and unpredictable. That's the reason for body armor, defensive weapons, etc. Sometimes things just go to crap and there's not a way to prevent it.