That was Arkansas Trooper Roger Perry, who told the FBI that he had received a call from Helen Dickey (Chelsea's nanny at the time) from the WH informing him, "Vince Foster got off from work and went out to the parking lot and shot himself in the head."
I'm quite sure that Trooper Perry was telling it as he'd been told. Either Dickey didn't quite get the story straight when she was told about it (we don't know who told her) or she was too stressed out to tell the story correctly when speaking to Trooper Perry.
Thanks for the confirmation. All this is very interesting and I hope one day to know the truth.