Hey Prime, I think the addage "show, don't tell" really applies here. Too much happens in this scene to use so few words. You wind up telling us George is a furious security guard who had his life threatened in Vietnam, Frank is the handsome, arrogant punk, branch manager who slept with his wife, and his unnamed wife is young and pretty. To show how this might go in a show, don't tell mode:

George Winslow disliked the term rent-a-cop. He kept his holster and shoes polished, and took as much pride in his bank guard uniform as he did in his Marine Corp dress blues when he served in Nam.

In two sentences we know George is proud, a bank guard who doesn't like his job trivialized, and a former Marine who served in Vietnam. Show the reader who they are by what they do, and how they do it. It's one thing to say Mr. Johnson was creepy and another to say Mr. Johnson used to stand in a shooter's stance and sight down his finger as neighborhood children rode by on their bicycles. He'd say "bang", and always followed up with "gotcha kiddo.". Let reader determine by what they have seen, whether the characters are arrogant, furious, or creepy. The more decisions you leave to your reader, the more they will love you.

Also, there are emotional scenes left untapped. How did people react to Frank being shot? Did they think it was accidental and Frank was just caught in the crossfire, or did anyone feel that George was gunning for Frank. Maybe a few were pleased Frank was shot. Was George seen as a hero?

Shootings are gruesome, disturbing events, but in your treatment it comes across as sterile. Emotion and detail are curtly glossed over with the words "blasted away the heads of both bandits". Readers should feel horrified and scared if you do it right. They should feel they're in the building. The outcome should be in doubt at least for a while.

You have a good sense of dialogue. This piece could use more.

I hope you find this at least a little constructive.