Giant Robber Fly

Gave a second suggestion based on Hunter Hebenstreit's comment. I think it is closer. You saw it, so you decide on the genus. Not able to tell the species from just one photo.

I think you are right. Its profile looks a lot like Great Bee Mimic - Laphria grossa, but it is hard to tell the details. So here is another bugguide.net link to compare: http://bugguide.net/node/view/21056

Are you sure this is not a Laphria sp.? One of the bee mimics?

I could not see enough detail to identify the exact species. Maybe some else will help. Nice catch of this one having lunch.