I do buy into the idea that he had some kind of FBI/CIA connection. Perhaps as an informant at one stage. The way the FBI have been speaking to the public about him is extremely strange.

I can't personally see the shooting as a 'sting operation' gone wrong. I think he was an international arms dealer who simply got mixed-up with a dangerous group of people. His massive gambling transactions (laundering) and wire transfers to the Philippines give credence to this. Also, he apparently left the country frequently without explanation.