its a robber fly, eric. more specifically, a giant one from the genus "promachus". google it, youll find that they can be pretty nasty.
heres some research ive done for you. interestingly enough, its also called a "bee-killer fly".
http://images.google.com/imgres?imgurl=http://bugguide.net/images/cache/SKUKZKNKMKO09QA0PQLSUQJ05KDKMKVKIKZSBQ309QLSAQTKMKCKMKZSPQZS5KBKAQZS7KAK7K1KIKLSVQHS8KJ0.jpg&imgrefurl=http://bugguide.net/node/view/27868&h=429&w=560&sz=26&hl=en&start=11&um=1&tbnid=xGzw2OV6w_YTOM:&tbnh=102&tbnw=133&prev=/images%3Fq%3Dbee%2Beating%2Bfly%26um%3D1%26hl%3Den%26safe%3Doff