An angry bee flying at my window for an hour?

just over an hour ago i got home and found a huge huge bee in my room id left window open all day, it eventually left through the window. For the past hour it has just been flying at the window and bashing itself against it , crawling on the window ledge trying to find a way in.. theres gardens full of flowers round here ut it seems intent on staying at the window.. its getting very angry and doesnt seem to be giving up... ive never seen anything like this.. any ideas??.