I think the source of the claim was the Father of the girl in the car. He apparently made statements on a radio program that his daughter had begged the FBI officers through this long delay during which the young man lay handcuffed on the ground.
I don't know if, during the medical attention at the scene, the man remained handcuffed or what. But I can imagine that it would seem like forever if you are laying there watching your loved one like that regardless of how long the delay actually was.
I don't know anything about it myself, but the fact that these turds left a seriously injured young man handcuffed after determining that he was not even armed makes me furious. All these arrogant pricks had to do was to listen to a police band scanner. Someone in the chain of command of this gaggle of clowns failed to communicate with the local LE and the result was this shooting. Of course, I'm giving them a real break by assuming that much.