Solution—The Killer

The getaway driver is not Rex Bender (2), Joe Kreble or Dick Doran (3), therefore the driver is Tony Faracchi. The driver (Faracchi) is not the murderer (4). Rex Bender is not the killer (2 & 4). Dick Doran (5) is not the murderer, hence the man who shot the bank cashier is Joe Kreble.