Name that gangster movie!

[Theory5]

A while ago I was watching something on gangster films or 50's films or real criminals made into movies or something and I saw a movie I wanted to see but I forgot the name. I thought it was bonnie & Clyde but they didnt fit the description. They showed a clip where the two guys walk into the bank with tommy guns and one guy politely says hello to the cop like he was just passing by in the street. Its a long shot but does anybody know it?

[adobetony]

do you have any details that go beyond this scene?

[suresh123]

If you provide more details,I will tell the movie name but 50's movie it is very difficult task so please describe more about the shot.

[webcreations]

Never seen this..

[genraven]

I don't think I've watched any movies that were from the 50's.