The car scene at the end- SPOILER
a follow up to the "did Sonny sell out Sal" thread: I just watched this and was curious about how the FBI agent got access to the gun he shoots Sal with. Earlier in the bank, Sonny confiscates a handgun from someone which led me to believe that Sonny plants that same gun in the limo when he's doing his 'search', so the FBI/COP could access it. So I believe yes, he did sell out Sal.
Or am I reading it incorrectly?